Originally Posted by grolby
Actually, it's really mostly fashion. A quick-release hub is quite capable of holding a fixed-gear or singlespeed wheel in place. However, track bikes use these big ol' nuts to hold the wheel on, so that's what's popular. Add to that the fact that too many people don't know how to adequately tighten a QR, and the belief that a QR somehow won't hold a fixed wheel tightly enough was spawned.
So, in sum, the answer is: fashion and a misguided belief that a QR isn't good enough.
It actually depends on the quality of the QR. I remember buying these fancy QRs from some Ti manufacturer on closeout. Yep, stupid upgrade from the cheapie Shimanos (that worked fine!).Turns out that the wheel kept slipping, no matter how hard I tightened down the QR. So, I ended up putting the old QRs back on. YMMV