Why could you possibly want it there?

Because a) it's easy to use, and b) that's how many other car stereos do bass/treble/balance/fader and people expect it that way. For instance, the factory stereo on my wife's Honda works that way.

Now, if we could actually get bass and treble into that mixture, a real bass and treble commanding the DSP (not stealing any EQ bands to do the job), I'd be a really happy boy.

How often do you use the fader controls?

Frequently. I rarely use the balance, but I frequently use the fader. At the moment, the fader controls my subwoofer level. Before that, when it really did fade front/rear speakers, I would adjust it when passengers were in the back seat so the speakers didn't blast right behind their heads.

And if there was a bass and treble in there, I'd mess with it even more often, adjusting the amount of general bass to compensate for changing amounts of road noise.

Have you ever accidentally changed them?

Yes, a couple of times. Very rare thing. Easy to see when I've done it, easy to correct.