Why does collecting a UK train ticket require you to insert a card?

This answer is only speculative.

The first thing to note is that train tickets can be quite valuable. For instance an "Anytime" fully unrestricted first class return from London to York is £365. This is not even close to the most expensive ticket on the network either, but in this case (unlike say unrestricted first from Penzance to Aberdeen, £660*) London-York is a key trunk route and no doubt many of these tickets are sold and collected each day. Since these particular tickets are refundable, they could in principle be worth close to their face value for cash. I am not sure if you can purchase carnets for delivery by machine, but if you take advantage of the five-for-the-price-of-four offer, that would be a delivery of value nearly £1500 on London-York.

It makes sense to me, particularly given the politics at British Rail and its successor companies, that further identification is required when collecting pre-bought tickets. ISO/IEC 7813 standard globally mandates that payment cards, including credit cards and perhaps some supermarket loyalty cards, store the name of the cardholder in a specific place on the magnetic track. Therefore, the cardholder's name can at least be verified. Have you tried collecting using a card registered in someone else's name?

It may be that the problems caused by expired cards, forgotten cards, or other such matters, particularly at unmanned stations, make it (quietly) preferable that the machines not enforce full validation of the card number. It may be that the information on the card is merely recorded so that in the event of a stolen ticket, there is at least a paper trail potentially leading to the culprit. Or it may be pure theatre, as elsewhere suggested.

*This ticket isn't even the most expensive, since it doesn't allow travelling via London, but I was unable to force the via-London route.

Often, it does need to be the card used in the booking - I've never noticed any obvious pattern to when it does and when it doesn't or which companies do and don't, but I think times when any card is allowed often involve tickets booked through 3rd party agencies.

As for why you'd ever require a potentially unrelated card, there was an incident at an old workplace of mine which might explain the issue - basically, it helped clear up confusion when multiple people were involved in one booking, which is the sort of situation that could happen often and be disruptive at a busy station.

There was a senior member of staff who was very good but a bit... absent minded. Her personal assistant was super-efficient. They booked some tickets in her name to go to some work event, using a company card. The super-efficient PA swung past the station that lunch break and picked up the tickets, using her own card as ID, and told her that she'd meet her at the station on the day of travel with the tickets, briefing papers, etc (an arrangement the senior staffer promptly forgot).

On the day of travel, the senior staffer turned up at the station in a rush, tried to print off the (already printed) tickets, which didn't work, and flew into a rage at the nearest member of staff. They checked that she was the right person and had the right code, and then gave her the time, date and name of the person who had printed her tickets. Embarrassed (I presume), the senior staffer muttered something like "Oh, that's my PA... oh, there she is, waiting for me... Sorry, excuse me", met her PA, and collected the tickets.

Key points:

• People often need to collect tickets booked by other people on cards they don't have, especially for business travel or when booked through an agent or company travel centre.
• People often won't realise someone else has collected their tickets for them (or might even forget they printed their own tickets), which can result in stressful confusion that can be easily resolved by telling the customer the name of the person who printed the ticket.
• Scanning a random card is a non-foolproof but quick and easy way to (probably) get the name of the person scanning the card. It's not robust to someone trying to deceive the system, but (I believe) it's not intended to be. If this is indeed typical (and assuming I remembered it right), it's for clearing up common confusion, not preventing fraud.

Also, sometimes I've had tickets auto-print the moment I enter my card, without asking for any code. I don't know why this happens some times and not others - maybe it's only at peak times to reduce queues, or some train companies do it but not others... but it seems like sometimes, the system works on a "ask for code if card doesn't match, just print if it does" basis.

I have read these answers extensively and can't really find a justification for having to use a card, whatever it is. I have travelled by train in other Countries and never have I had to swipe any card. I can understand being asked the same card as the one used for booking, but as some people have said, any card will do.

So the only reasonable option my mind is left with is that Network Rail collects information regarding who accesses train stations and where they travel to/from. One possible use for this information, apart from business intelligence, is tracking potential suspects, if requested by the police.

From a security standpoint, a reference number seems enough to me, and I don't see how swiping a card, whatever it is, could protect you from having your tickets printed and used by somebody else.