Please stop the insanity wrote:
They are more comfortable and appropriate.
I certainly don't think tights are inappropriate, but I never wear them unless I'm riding a bike or using them as a base layer in bitterly cold weather. (Racing would be a third exception, but it would have to be "frostbite cold" before I'd wear anything other than shorts in a race.) To each his own, but I find all the "almost tights" track pants to be much more comfortable and just as functional as tights.