I am about to buy a jazz bass and I see the basses with pickup covers and the ones without. They look really snazzy and pretty, but I was wondering if they have any real purpose, and if not... why are they there? Also, does anyone play a jazz bass that has the covers, and do they get in the way at all?

I personally find them ugly looking, but that's just me. They were popular in the 60's and early 70's. I have played the same bass with and without the covers, and they sound almost exactly the same.
Apparently they affect the magnets in some way to pull out more high-frequency. But I've never noticed it.

I personally think they look good; I wouldn't take them off.