As I have said previously, public transport needs to be accessible for all.
Whilst handling cash can be expensive and time consuming for operators, I think the clamor to go cash free may have a negative affect on some passengers.

I don't know the exact numbers, but if I remember correctly, there are approx 2m people in the UK who don't have access to a bank account.
There is also a proportion of the population who have a basic bank account, which usually gives access to a basic debit card, similar to the old Visa Electron.
In most cases, it can't be used to make contactless payments.
I witnessed this just the other week on a Northern Rail service. The conductor showed some discretion and let the passengers off with their payment.

As we know, in London, they have the 'universal' and established Oyster card. It is possible to top it up in a range of locations, in a manner of ways.

Until operators in the NE start to adopt a uniform card like Oyster - which can be topped up in a range of methods and is accepted on each operator across the region, then I don't think cash free buses are an option.
There is the PoP card of course, but operators don't tend to push this. They push their own systems.
Nexus seem to have gone quiet on the PAYG PoP card, after the initial launch and fanfare.

So whilst it might be easier for some to pay contactless, there are a fair few who won't be able to access public transport at all, unless vast improvements are made.