That's very true Mike, however stuff can still get uncomfortably wedged between the top of the gaiters and your legs and work it's way down, especially the little slender, poky grass seeds that are everywhere around here. It's like a torrential downpour of stuff falling on your legs and shoes in the grasslands around here. Gaiters with shorts are a lot better than nothing though. Also, there are plenty of poky plants and thistles which make shorts very uncomfortable. And even wading through dense grass for long enough can rub your legs raw. I suppose if you walked through nasty stuff in shorts for long enough, the skin on your legs could toughen up.
When I go hunting with my dad, he usually wears high top boots as a solution. I wear vivobarefoot aquas with those tan REI gaiters.