Answer:
*actives have less hum which to an unexperienced player they wont hear it
*active pickups are easier to swap, unplug the pickup, put the other in sort of like a video game controller... no wire soldering skills required.
*there are 100s of passive pickups and only few actives pros use
*passive pickups are cheaper
*passive require no batteries like actives
*passive pickups are cheaper to swap out (less work required is the reason)
*passive pickups don't sound as sterile as say EMG pickups , blackouts are more real sounding though.
to reduce hum look into pickup covers and copper shielding tape