There's also the state v. federal political issue of the interstate commerce clause. Some municipalities in the pretty far past have tried to restrict people moving there by creating onerous registration barriers that were then struck down by the feds. They're allowed some leeway there, but there's a limit that they don't want to push and the feds are more than happy to enforce their power.

My state (CO) semi recently hit a morph of this concern because they had "pioneer" license plates that cost an extra $100 or so and were only available to people who could prove N generations of ancestry in CO. The feds struck that down as .gov services provided being dependent on state origin and therefore against the interstate commerce clause.