Personal Taste. Jerry Garcia, Paul Gilbert, and hundreds of other musicians used DiMarzios.

A certain breed of guitarists love the ToneZone pickups, some love the Super Distortion Pickups, Some love the PAF's, etc.

Think about the world of Humbuckers (outside of stock pickups): Who are the Major Players?

Seymour Duncan
DiMarzio

There are others, but the ones that stand out the most are Duncan and DiMarzio.

~Incidents