Nelowulf
Well, consider that people like to keep to the planets they know. Sure they're scattered, but its a lot better to know what planets they have if everyone knows what the planets are rather than simply sticking to proximity of the things.
Plus, granted, Hoth and Dagobah are within Bespin's vicinity. Still, what have either to offer a fledgling resistance movement?
I somehow doubt that a few wookies throwing snowballs would be much of a detterent! xd