Because of sound economic reasoning? And because of huge institutional problems too of course.
I'm afraid it would be fairly difficult to explain exactly how the system works in Belgium though, it's very complicated. In essence you could say that it's based on the assumption that there are three major groups: dutch speaking, french speaking and german speaking. The law sort of assumes that these groups have conflicting ideas of how the country should be ruled, so there's all kinds of protection mechanisms that ensure that none of the three groups is set back. This in turn means that for almost any political decision, you need the consent of the two other groups. And that's what's difficult.
However you should know that this is oversimplifying things.