I once heard a shiur about hair covering. Many people have asked why hair changes after marriage. One reason is that it’s mentioned somewhere that the koach that hair has (which isn’t easily explainable) changes when the woman is no longer a besulah. After it changes, it needs to be covered. We assume that after marriage, this is the case. However, at the wedding itself, we don’t assume that, and she doesn’t have to cover her hair until the next morning.
