Thanks for posting this. All the comments about "easy win" and "bans" made me a bit laugh but didn't want to bother answering.
You can use whatever controllers you want in tournament as long as they don't offer unfair advantages (which Hitbox don't have).
For example a french player (
Olivier "Luffy" Hay) always plays with a PS1 controller (and won Street Fighter 4's EVO 2014 with it)
I don't see the point of setting Hitbox aside from the others options.
On a regular controllers some peoples will use D-pad, others analog stick. Then some prefer Arcade stick (and here there is again some choice on the joystick). Then some others just wants pushing buttons with a hitbox (which is just a bother layout for D-pad basically).