Originally Posted by Trackliche

Because it sounds way more awesome to say "ninety eight" than "forty eight thirteen". Helps weed out the roadies.

But for real, I think it stems from the early Penny Farthing-style bikes: the pedals were directly connected to the front wheel, so the "inches developed" was just the diameter of the front wheel. The manly men racing those bikes would compare dic er. . . wheel sizes in inches developed. It stuck.

TC