what other purpose is there? j/k. Nope they're just for looks. But they can be a pain if you're used to playing right over the pick-ups.
Yeah, i just ordered a fretless SX 62 jazz bass that comes with covers. I usually rest my thumb on the pickup, so resting my thumb on the covers might be wierd for a while. If i dont like em, i can always pull them off i suppose.
I play a MOM jazz, and i always play with the neck pick up cover on..like Marcus..but ill usually on ever put the bridge on one if i put a foam mute and want to hide it. I also ordered a SX, but i just got the fretless in lake placid blue, and im thinking abut just getting a neck cover for it, because i love the way the look.