What's the point of having a Good To Go! pass aside from avoiding the extra 25¢USD/trip?

Seattle-area resident (and frequent Good To Go! user) here.

Good To Go! works a bit differently depending on the context in which it is used. You can explore each use case here. In summary, there are five different situations where tolls are collected, and the advantage of a pass is a bit different for each.

I-405 express toll lanes: The toll rate changes based on traffic conditions. The lanes are equipped with license-plate readers. If you do not have a pass and have not registered your license plate, you will be charged by mail the posted rate plus $2 regardless of the number of occupants in your vehicle. If you have a Flex Pass, you can either avoid the $2 surcharge as a solo driver or avoid tolls altogether if you have the minimum number of occupants in your vehicle (2 or 3 depending on the time of day). Motorcycles can use the lanes for free with a motorcycle pass. Sometimes the posted rate is FREE, in which case no vehicle is charged a toll, regardless of the presence of a pass.

SR 167 high occupancy toll lanes: The toll rate changes based on traffic conditions. Since there are no license-plate readers on these lanes, it is not legal for a solo driver to use them without a pass, except when no toll is being charged (FREE). Any vehicle with 2 or more occupants can avoid tolls with a flex pass or use the lanes for free with no pass. Motorcycles can use the lanes for free with or without a motorcycle pass.

SR 520 bridge: The toll rate changes based on the time of day. The bridge is equipped with license-plate readers and charges tolls in both directions. There is no change in the toll with the number of occupants in the vehicle. The surcharge for paying by mail (via license plate) is $1 times the number of axles.

SR 99 tunnel: Same system as the 520 bridge. The toll rate changes based on the time of day. The tunnel is equipped with license-plate readers and charges tolls in both directions. There is no change in the toll with the number of occupants in the vehicle. The surcharge for paying by mail (via license plate) is $1 times the number of axles.

Tacoma Narrows Bridge: Toll rates are fixed in time (aside from periodic announced increases) and only vary depending on the number of axles. Tolls are only charged eastbound, with no recording equipment present on the westbound lanes. There is also the option to pay with cash or card at a toll plaza (the only one in the state), but it is $1 more expensive over a pass for a two-axle vehicle, up to $3 more expensive for six or more axles. The surcharge for paying by mail (via license-plate reader) is $1 times the number of axles over the pass rate.

Notes: For all cases except SR 167, if you have registered your license plate with Good To Go! but do not have a pass, the surcharge is $0.25 on top of the posted rate regardless of axles or occupants. Registering (pass or not) avoids the hassle of paying by mail and the possibility of late payments with the associated additional penalties. If you have a non-flex pass, you will be charged the posted rate regardless of the number of occupants in your vehicle, excepting motorcycle passes. The flex passes work a bit on the honor system (the vehicle occupants can change the mode to and from HOV at will) but it is possible to get caught and fined for the wrong setting.

A cursory glance of the GoodToGo! website that you link to shows that:

With a GoodToGo account:

• You save money
• Toll fees are automatically deducted from your account (either pre or post-pay)

Without an account

• Costs more ($2 higher per toll as per the website)
• Bills are mailed to the address that your vehicle is registered at

And of course if you fall to pay a toll (Because EG your address is wrong, or the bill got lost in the mail), you are subject to civil penalties and potentially a hold placed on your vehicle registration.

So if you want to waste money and risk the possibility of civil penalties, then no need to create an account.

And the GoodToGo sticker seems to be a form of RFID tag which makes any comparison to the license plate reader non-sensical.

Reddit user doktorhladnjak mentions the reason why the pass is financially recommended whereas the "Good To Go!" lanes/tolls seem to have the ability to read license plates:

Sometimes their software can’t determine the license plate in the photo so a human has to look at those to determine the plate number. Sometimes the photo doesn’t have a clear number at all so the revenue is lost. Because of that, you get charged a higher price for not having a sticker.