Although public transport always caters for paying in numerous ways, it can be hard to get people to change habits and it can be hard to get new customers to pay the 'easy' way. If you don't get a bus very often and don't have cash on your person, it can be worrying or slightly intimidating even if you just have to tap in and tap out. Plus you have to link a payment card to your phone.

Personally I am still a paper ticket person, psychologically I need that bit of paper.

Top tip if visiting the UK and going outside London with a ticket bought online or with an app - always screenshot your purchase!