Then why paint them (including tops) at all?
I brought that very inconsistency in my thinking up in an earlier post, just for fun. But I have my reasons, and here they are:
Rosewood is an oily wood that doesn’t need a finish. Play it for years and years, and it stays nice and smooth. The natural oils tend to resist dirt and detritus.
Maple and mahogany do better with a finish, even if it’s just an oil finish; otherwise they become furry, can even get splinters or develop cracks from stuff like sweat from your forearm and hands, and entropy has its way with them much sooner. They also tend to absorb dirt and grime unless finished.
Put simply, it makes more sense to finish maple and mahogany (and many other hardwoods), and it makes sense not to finish oily tropical woods like rosewood.
And if you look at historical instruments, you’ll see that most going back a very long time have the more perishable woods like maple and spruce finished in some way, and leave the less perishable woods like ebony and rosewood unfinished. Seems to me that people who make instruments do things for hundreds of years for good reason.
So that’s why I make the distinction.
I certainly understand the aesthetics issue; on the other hand, I’ve bought 3 PS guitars with Madagascar rosewood that’s lighter in color than IRW or BRW (it’s got more tan coloration), because the stuff sounds great. I’d never dye it.