Quote Originally Posted by Torrilin View Post
I'd bet on "can't fit a rack". Not all bikes have braze-ons (bike-speak for "screw holes") for a rack. Good sturdy racks for groceries need to be screwed onto your bike in several places, and most of the ways of attaching a rack without screws just aren't very sturdy.

A touring bike will at least have braze-ons for a back rack, 2-3 water bottles and a frame pump. Usually they'll be set up to take fenders, a front rack and both skinny slicks and fairly fat knobby tires too. They're a good choice of road bike for normal people because of that.
Thanks for the detailed explanation. My bike has all of these, so now I understand why it is more suitable for commuting than a road bike.