JFK air train is nice since I can use a credit card to pay for it and then get a metro card using credit card. I’m sure that is Hugely advantageous to foreigners that haven’t gotten US dollars. Most busses have to use cash or metro card that you must purchase somewhere else.
San Fran Bay Area finally went to clipper card for all transit. So I can use the clipper card in east bay busses without worrying about exact change like I can for subway and sf busses and cable cars.