The US has busses like that too. They drive bus routes that keep them on the main roads, instead of going into all the residential backroads and side streets where they would get stuck. Do you think buses just drive whatever route they want, without any forethought? Actual planning goes into that route, not just for getting people from A to B, but also for ensuring the bus is physically able to fit. And school busses simply use different dimensions, to be able to expand their potential routes.