If you’re wondering why time based charging is so prevalent here measurement Canada has only just recently allowed usage based charging on some currently deployed charging stations. https://ised-isde.canada.ca/site/measurement-canada/en/buying-and-selling-measured-goods/electric-vehicle-charging-stations

The (possibly oversimplified) gist is that the providers that want to provide usage based fees would have to pretty much certify their equipment on the same level as utilities providers which is expensive to do. The workaround is to charge time based fees. ¯_(ツ)_/¯