[mcv]

Probably because your country doesn't have as many bikes as Netherland does.

In most places in Netherland, parking wherever you like is no big deal, but there are places (train stations in particular) where bikes really need to be restricted, or there'd be no room for anything other than bikes.

It's the same as with cars: the occasional randomly parked car is not a big problem, but once you've got thousands of cars being parked all over the place, it becomes time to restrict them to designated parking spots. It's no different with bikes, except you need a lot more bikes to get to the point where they become a problem. Dutch cities have that many bikes.