In days gone by thats correct, the logic being you would always have atleast one front brake, as a car would likely skid of only the rears were working. Cars moved over to a front/rear split when front brakes became more and more powerfull and required different valving and/or different(usualy split) bore master cylinders, the result being you simply couldnt have a front and rear brake on the same hydraulic circuit.

For a few years small commercial vehicles in the uk atleast, had a front rear split, but the front callipers had two sets of pistons each fed off a different circuit, so regardless of what circuit failed there would always be front brakes! was a pain to maintain with two brake hoses, 4 pistons, and 3 bleed nipples per calliper!