It isn't only cosmetic. It can be technical too. How do you clean a multi ganged, multi position selector switch that most of the older rigs used to have? It isn't easy, short of total replacement. And it doesn't stop there, either.
Absolutely true. Dust will combine with the cigarette tar to form a composite on components that's impossible to fix. There's more to ham radio than inheriting and correcting the problems from someone else's disgusting habit.