From the Wikipedia article. It's not like BASE is illegal overall here in the US either, we still have Bridge Day and such.
You hit the crux of the argument though, some parks don't want jumpers because they represent an inordinate drain on their resources and risk to their personnel.
It's a lot like illegal drugs. It's a fun activity that's bad for the participants and exposes external costs on society. Seems like the standard solution of "legalize, tax, and regulate" would also apply here. Rather than simply ban these activities, maybe they should be made to bear the costs of rescue, either by putting liability on to them after the fact, or charging a fee up front.
What I was trying to say was: In Norway they say, don't jump here please, jump over there.
The reasons in the wikipedia article are no longer valid apart from the instability of the wall and talus.