That makes sense. It would be silly for kids to show up wearing hats advertising a presidential campaign from 15 years before. On the other hand, it's very easy to change the character's appearance. On the third hand, I think the kids might still pass the hats on to their progeny for generations to come. By then, they would have become family heirlooms!
So: If anybody downloaded those hat-hairs, note that they are not binned, and see Rose's tutorial on how to do that.
I suspect that the guys at Maxis were thinking that people would want custom hair colors to be inherited. Adding in options requires more programming time; hence, cost, and there's no competition to drive them to excellence.