Someone asked me why their car's front brakes always seem to need replacing long before the rear brakes do.
I started to give him the old "inertial weight transfer to the front while braking" reply and then found that it really wasn't making total sense to me.
Providing you don't drive and brake like a madman neither the front or rear tires are doing much skidding on the pavement so it's likely all four are all making the same number of revolutions while braking. So, if the brake pad areas and the piston diameters were all equal front and rear I'd expect the pad wear rate to also be equal.
It's been too long since I've done a DIY brake job and I never stopped to study the relative sizes of drums, shoes, pads and pistons back when I used to do that stuff on all our family jalopies.