Would a non-business traveler ever benefit from collecting air miles, as compared to simply buying the cheapest ticket available?

There are three things that set (some) frequent flier programs apart from other rewards programs. How important these are to you may determine whether they are worth doing.

The first is "Status" which you refer to by mentioning business travellers. Never lining up, spending an hour or more less in the airport than others, waiting in the lounge eating and using free internet, and getting upgraded for free are all pretty cool. But unless you fly an average of a thousand miles a week, (50,000 a year) you aren't getting these and can ignore them.

The second is that miles awarded don't always correlate with money spent, enabling silly things like "mileage runs". This makes it impossible to say that your program gives you 1% or 2% or 0.5%. A person who makes long direct flights between popular airports will get a higher percentage back than people who make connecting flights involving less popular airports, because they're spending more money but getting the same miles for it.

The third, and the only one that applies to me, is that redemptions don't always correlate with price. (I'm not talking about those travel-only credit card reward things that go on about any airline any time no blackouts - those are just a dollars-for-points redemption. If the price doubles, the points you need double.) Airlines still exist with redemptions where the points come from a chart. This means, for example, that Toronto-Vancouver-Nanaimo costs the same points as Toronto-Vancouver, even though a paid-for-ticket might cost almost double to add on that little local leg. It's also pretty common for business class to cost only 25% more points even though it might cost 5 times the dollars. This let me do Toronto-London-Venice-Toronto, all business, for barely more than Toronto-London-Toronto in economy, and treat my mother to a number of business class flights and three days in Venice.

I used to chase status, but the programs changed a lot and I no longer find it worthwhile. I choose the flight that's best for me, whether I'm paying for it or my client is. Because of where I live, it's often on the airline I collect points from, and I collect them when I fly that airline. I look carefully for redemptions that save me more than a penny for each mile I spend - two is even better - and use those when I can. As I mentioned above, tickets that would cost the same dollars don't always cost the same points, so I never assume that a redemption is a good deal. On my own recent epic trip, I flew on the airline that I collect on, but for several legs I paid $50 less not to get the miles. I did the math and they weren't worth $50 to me.

My advice? Sign up for frequent flyer programs, but don't let them drive your decisions. As the points pile up, look at how to use them, but keep a spreadsheet handy. Little actions like using one chain of gas stations because they give you miles, or one drugstore because it gives you miles, are harmless enough if you like that chain anyway, but don't go out of your way to accumulate miles you may never use. And never pay extra for a flight that earns miles, whether that's a charge on your airline or the price difference between two airlines. Keep them mentally filed as a bonus gift some folks give you, not as a motivator that you chase, and pay for with time and money. You'll be happier and have more money, too.

tldr: If you travel once or twice a year, on full-price airlines with frequent flyer progammes, sign up for them. But don't obsess over them, and focus on price and other benefits first.

Longer answer:

As always, it depends.

Many (most?) budget airlines don't have a frequent flyer programme (or at least one comparable to those on full-service airlines), so if you mostly fly on those, it will take a long time to acquire enough miles to do anything useful. Some airlines (ahem, Lufthansa) also have a nasty habit of "expiring" old miles, even if you are still actively flying with them from time to time, so definitely avoid those if you don't travel (and redeem) often.

It is true that if you are only flying for leisure, miles will probably trickle in slowly, whether you plan to fly budget airlines or not. As such, you probably won't get much/any elite status levels, and the benefits won't really be relevant.

Incidentally, I think you are wrong about some of the benefits - lounges are very useful even when not on a transfer (most of my flights don't involve a transfer, but I still use the lounge before virtually every departure, since getting through security with no time to waste but never missing a flight, consistently, is virtually impossible), and they do cost a lot - in fact for some airports (e.g. Heathrow T5 until recently) didn't have the option to pay for them at all.

It all depends on how frequently you travel and what type of travels. If you just perform 2 domestic flights every 2 years, then miles collection isn't worth... If you take more than few flights every year including some long distance flights, then it is worth, even in economy class, even with the cheapest ticket.

To give you some figures, with some airlines, 2 round trips from USA to Europe (so 4 flights) would allow you to collect enough miles for a domestic flight.

Then, miles collection doesn't cost anything as long as you take the cheapest ticket so there is no reason to avoid it... But again, this is really dependent on how frequently you travel. If it is once every 2 years, not worth as your miles will likely expire before your next flight.

Unfortunately that is difficult to answer: About two years ago a large part of the industry (United, Delta) shifted the accrual from "miles flown" to "dollars spend" with a very complex set of rules. These programs are now pretty much useless for the occasional flyer.

Other ways to earn miles are associated credit cards. These offer miles for dollars spend and still have a pretty good accrual rate.

Typically a domestic round trip saver ticket costs 25.000 miles (United, American, etc). That used to be three round trips to Europe or two round trips to China or less if you have premier status with the airline. Today this calculation is a lot more difficult and depends on the individual rules of each airline.

There are also credit cards which give out cashback in the form of air miles, however their pay-out is usually lower than simply getting a fixed cashback in dollars.

Aeroplan points exchanged for international business tickets can be worth 4.5-6CPM and if you manage to find an upgradeable ticket it can be 10-12CPM. I've never seen a generic cashback above 2% , some special card+store combinations perhaps 4% but even that's rare. By churning and using Aeroplan cards I collect enough points to fly to Europe twice a year in comfort.

My strategy as a non business traveler is to have a few accounts with airlines that I know I will want to redeem miles with and that have a good airline alliance/code share program.

For example, I have a mileage account with American. I fly quite a bit with American as well as US Airlines and Alaska. Then I use the miles collected with these airlines towards reward travel with American.

I think you should evaluate all airlines for each major alliance (Sky Team, One World, Star Alliance) and create a mileage account for one airline in each of the three. It only makes sense to have one account per alliance since you cannot consolidate the miles (maybe possible but at a cost).

Additionally, there are a few airlines that do not participate in any alliance (like Iceland Air, for example). You should only join those mileage programs if you intend to travel with those airlines more than once a year since otherwise your miles will expire anyways.