Well,
Fender was quite simply the first to hit the market....everything that has come after gets compared to the yardstick that is Fender....it's hard to fight 50 years of marketing and image
Producers and engineers know what they sound like and know what to expect from them as we have had 50 years worth of recordings to prove it....
that said i wouldn't use an IBM from the 1960's currently as that design has been seriously improved upon....now before you say i'm comparing apples and oranges i'm not....we have learned a lot about ergonomics, electronics, physics, acoustics, sound waves, etc. in that last 50 years....
I don't personally like Fenders as they were shoved down my throat in shool by our teacher....because to him there was nothing besides Ampeg and Fender.....
I don't like their necks or their look myself (with the exception of the Jazz and i don't like it's overall sound) when i was turned loose the first thing i did was to buy a B.C. Rich and a Hartke amp...(hey it was the 80's)
I have owned lots of basses over the years including many P's, J's, and PJ's, but I have never kept them long...even owned a few Stat guitars as well.....didn't keep them either...
My first reaction when i see a guy playing a Fender and an Ampeg amp in his back line is not a good first reaction....
but then again it's kind of like the Whole Sabbath argument....Without Sabbath no Metal.....
Without Fender......well you get the idea
however just because they were the first does not make them the best.....nor does it make them the worst...I simply believe that there are much better products out there for the money...
there are many many many bass companies out there....pick one that appeals to you if Fender doesn't and quit stirring up the sheep and the cattle....

lol i jest (sort of)