I think that there is a real reason, and it has to do with long chainstays on older bikes (which, apart from ride characteristics, helped allow getting the wheel in and out of a frame having both horizontal dropouts and fenders). Once the fender is set to have clearance in front of the wheel, it looks funny if the clearance at brake bridge is much closer, so additional clearance was provided there too. Result: you need a longer reach brake in the rear (how much? Oh, about 14 mm according to Weinmann). Without fenders, the "roughly equivalent clearance" problem isn't really a factor; so the brake bridge can be lowered, as it is on many bikes that followed the "please, no fenders, we're not British" fad.
Last edited by Charles Wahl; 08-13-12 at 07:59 PM.