A small update on this thread from something I came across at the weekend, specifically in regard to customer behaviour.
Preston Bus vehicles (well, at least one of them!) carry a notice affixed to the Covid/Assault screen which says (punctuation as in original!):
Customer Notice
If you are using our Tap&Go facility. Please present your card on the machine.
If you are not using Tap&Go DO NOT present your payment card until requested, by the driver.
This seems to me to be quite a useful way of realising there is a "problem" (albeit, as stated upthread, stemming largely because there has been no major new ticket machine since the widespread acceptance of contactless) and trying to educate customers in the best way to go about using their card. Much better than the lottery of "yes, no, not yet" that seems to prevail in many areas. Of course, in areas that do not have a tap/go type facility, the notice could be worded even simpler.