I'm of a mind if that if you like to mod just for fun, go ahead and mod to your little heart's content, you don't really need a reason other than you enjoy it, but what kinda bothers me is when I see someone proclaiming, "I'm getting brand X bass in a few days ,and I'm gonna change the pickups, tuners, bridge (BA II yet again), etc." Why? You don't even have it in your hands and you're basically gonna change everything on it without even playing it once? Before you know for sure it actually needs it? That makes no sense to me. I get the impression a lot of times some are doing these (same old, same old) mods just because they get the idea that's the way you'e supposed to do it in order to get a really good bass. The never ending quest for the perfect bass, I suppose.
Myself, the extent of my mods are fairly superficial, straplocks as a matter of course, A black pg replacing the white one on my MIA Jazz, Jazz style black knobs on my Squier VM J, thumb rest, bridge covers, all minor stuff, none of which are the major functional components of a bass. They just don't need them. The only time I will likely change anything like that is if something breaks. The only exception might be my SX, the electronics in that are kinda iffy, but then again , I may not do anything to the SX unless it gives me reason to.