I find this interesting. Once upon a time I was involved for a while in small town road and parking planning, very complicated and many factors most wouldn't think of (delivery needs, noise, pollution, rights of way, emergency vehicle access and more).

I haven't heard of anything similar to total motorbike bans anywhere else in the world but I don't have a broad knowledge. I think in UK and Aus such ideas can start at local government level and spread. Often such local government regs, ie parking, vehicle access and times can be far away from the usual major political party positions, a local quirk because of local conditions such as in London.

The nearest thing in Aus so far is toll roads which no-one likes but which are growing and necessary if you want fast access into major city centers. So far you can always circumvent these routes but only by knowing the side roads and suburbs well otherwise you are forced into main bus/tram and local traffic routes. That may change over time if the idea of travel zones spreads. The need for safe streets for locals, often with residential parking and speed bumps etc. contrasts with the need for through routes, shopping centres and so on.

Do you have any idea why motorcycles are banned over there? Is there an official reason given and does it extend to scooters, mopeds and electric bicycles? Is it on all roads in a region including for locals in villages that surely rely on such transport or just in city centres and express roads?