I don't have any usable public transit where I live but the place where I'm familiar with it is Chicago and all the train stations have ticket machines. Bus stops no, but you can pay on the bus with a payment card, transit card, or an app. Cash fares are no longer accepted for some time.

I miss the old tokens they used to use. So simple, anonymous, easy to share with traveling companions, though could be annoying when you ran out.