I guess busses in London going cashless was the first time I was properly aware of the issues around it - largely that there are still a number of people in society who don’t have all their money just readily available in bank accounts. and I don’t mean people who don’t ‘trust banks’.
I saw this issue come up again recently when The Beer Shop in Nunhead announced they were going cashless. They said <20% of their transactions were in cash. Someone went in on them on Twitter about it (mostly in a ‘big banks are evil!’ way though) - in that instance I guess they ‘know’ that the people they are alienating are not necessarily their customer base anyway, but the point still stands that if all businesses were to go this way it would be a huge issue.