It might be a design decision regarding clearances. On my 58" atlantis I have 700c schwalbe big apple 50mm tires and fenders, and i gotta be careful with toestrike on the front wheel on tight turns. As you can see in my picture above, there isn't much room between the fender and the down tube. And this is on a 58"!!!
I can't imagine a smaller frame with the same geometry being able to handle beefy 700c tires and fenders.