I assume because those players want that tone. It helps that most Ibanez basses feel good and are above average quality for the price.
Saying you can get any bass to sound neutral is like saying you can stick an EQ on any amp/cab rig and get it to have a flat frequency response. It's theoretically sort of true, but you're going to be fighting against a baked in sound. If you want neutral you should start with neutral. If you want color, start with color.
Another way of looking at it is that if the bass isn't coloring the sound, it's not going to mask the technique of the player, for better or worse. There's nothing to get in your way, and nothing to hide behind either.
Completely agree - was basically going to say the same thing.