We now have the technology to be able to change that and, for the most part, bus companies are doing so. Tap and go has been less quick to get going but companies are most certainly pushing m-tickets and that is to be welcomed.
But most British operators, with a few exceptions, have failed to provide alternatives to cash or contactless payment to the driver for "single" journeys.
(I put "single" in quotes because most bus operators only allow the first part of a multiple vehicle journey to be paid at the start)
Metrobus and B&H provide 60 minute m-tickets in some of their urban areas, which is welcome, but even they don't have anything for their short hop tickets or for single tickets outside the urban area.