I believe there're two mainly reasons: Publicity Lower Price There's a question of tradition too. Talking about "sound", I prefer Music Man
ditto on the above also fender makes a gazillion different basses - MM makes 2 (not counting 5 strings and discontinued models).
like it or not: Fender = Industry Standard also they have cheap entry level instruments that actually play and sound good (more if modded) ps: I also looove MM
as those spectors are streamer clones . ps - i too am a music man man i have bad feelings about fender basses but won't bother trashing them as i know i am terribly outnumbered and will be pummeled into the ground if i start saying the things i truly think of them
Imho the answer is fender makes a passive bass and MM does not. Also MM are harder to control in a studio and sound board. I happen to like the MM bass alot, I just can't for the life of me get the exact tone from it I would want from it. MM basses have a modern sound and for people who want that that's great I think it's a great bass for playing outdoors where you can air out your amp sorta like the acoustic 360 of the 70's. The bass cuts like a ginzu and for some music thats too much where as my mia dlx jazz also cuts REAL hard but can dial in a very mellow tone, something I can't get a MM to do. I also think the amount of personnalization (pups bridges, pickguards) that can be done to a fender has a great deal to do with it.