Mind you, I'm not extremely clumsy, but I tend to drop things, bump into things, set things down in the wrong place so they fall, and so on.
A lot of my friends are clumsy too. I think this might be because coordinated people are spending all their time playing sports or riding motorcycles or juggling knives or whatever it is that they do, so we uncoordinated people end up hanging out together.
One thing I have noticed is that clumsy people tend to have really good reflexes, of a sort.
The usual scenario is this: you bump into a table, a glass near the edge falls off, you swoop down and catch the glass right before it hits the ground and shatters.
My theory is that since we klutzes are constantly causing problems, we get really good at fixing them.