Each bass is different, each pickup, even when the same model are different. My favorite pickup in one bass might not sound the best in another, and so on and so forth.
As I'm a natural tinkerer and problem solver, I enjoy the challenge of finding the right combination of parts to bring a bass to its true potential. For others this would drive them crazy.
Ironically, out of 20 basses, I only have three I haven't changed anything on, as they sound perfect as they are. One is a Spector, the others Jaco sig jazz, and an American standard V jazz. I'm still struggling with the other two jazzes to get sounding the way I want.