Before contactless was rolled out I used to use POP PAYG on buses all the time as it saved having to deal with cash.

I still have my POP PAYG in my work bag for the odd occasion I’d use Metro. Means I could tap in and out at barriers without having to get a ticket from the machines.
I’m looking forward to Metro enabling contactless on their barriers & validators, at which point I’ll be able to ditch the POP card, just like I ditched my Oyster when London rolled out contactless across all modes.