Originally Posted by Dave Mayer

Finally: a post that gets the core of the issue. Tubulars do not have to be as wide - useful air volume is the key. Tubulars, for the same nominal size have more useful air volume, as with clinchers, the space between the rim walls does nothing to protect the rim or cushion the ride. But the most important advantage of tubulars is that they are almost impossible to pinch flat, due to the smoother rim profile. Clinchers in contrast, have the 2 pointy hooks pointing downwards that are fragile, heavy at the worst possible place on a bike, and cause pinch flats.

So you can run tubulars at almost any pressure and not have the issues of pinch flats, rim damage. Or at very high pressures, the rim walls splitting apart and everything exploding.

So the real issue here is that clinchers HAVE to be wide with high volumes because they are susceptible to pinch flats, and the 2 hooks are susceptible to impact damage. Of course, wide rims and tires are heavy, have high rolling resistance and high aero drag.

Tubulars for the win all round.