I don’t know anywhere where you don’t need some form of ticket. Granted, various cities have different forms of convenience to make it practical.

In Boston, I know of some forms of transit that are free - because a specific business is paying for it to drive commerce, because the transit authority temporarily wants to promote it to reduce traffic, or because it’s undergoing a temporary change in operation and ticket collection would be inconvenient.

yeah it’s usually only like a dollar or two and takes a few seconds

guessing the 10-ride ticket costs more

you have to charge per ticket because americans are unwilling to raise taxpayer budget for this kind of thing