I have been looking at women's hair at work since mine started to fall out, I've noticed that they often have unusual hairlines. They often have low foreheads with their hairline quite close to their faces.
Also, their hair isn't often all that dense, and then they tend to wear it long. Often their front hairline can be quite thin for the first few centimetres.
So yeah, I guess just because they are women they don't have perfect hair. Have a look yourself, it is interesting too see the variations. Although don't get caught perving on their hair too much - just use the same discretion as when trying to look at their tits!