It's just the idiots that think bass is the only thing worth accentuating in music. Good music reproduction doesn't even enter most people's minds; it's all about more boom. Too bad what you get is a bunch of distorted, loose, low-end boom, and of course the audible-from-a-block-away rattle of license plate bracket, trim, mirrors, loose change, etc. It's perfectly possible to get a great sounding mobile audio system with good, punchy bass that underscores the music like it should and contributes positively to the mix. But most idiots don't know any better.
Considering the popularity of completely worthless one-hit-wonder music and the exorbitant prices people are willing to pay the megacorporations that own the artists producing it, it's pretty clear that most people don't give music much thought at all. If they did, they might realize that there's a whole fuckin' galaxy of talented bands who are concerned with producing consistently good music, and who care about their fans, not moving more "units" and making a 5,000% profit on their t-shirt sales.
Fuck corporate music and shitty sonic reproduction!