I think that to get the signal to the gearbox it has to go through the wheels first(of coarse),if they are bigger or smaller,it will change the amount of revolotions the wheel does.Think of it like diff ratio's.
I think it's because(don't quote me)the wider rims have messed the track.I heard that you can only go a little wider and still be in that track limit for that certain model.Oh and because there dildo's as well.
Just look at VL's.If you have sticky enough boot's and good sup setup I guess you don't need ATTESA,it's more weight to move.Also those 1000hp GTR's in japan only in 9's and the VL's are up with them.My 2cents.