This is part of an essay that a Rav wrote (who teaches the topic):
“Have we lost all sense of why the Torah (as explained in Kesubos 72a-b) forbids women to expose their hair to other men after marriage? Do our bnos Yisrael have no idea that exposed hair after marriage is a tznius violation because her hair is attractive to men? Do they think hair covering is a Chok like shaatnez?! Do they realize that the Gemara gives as the consequence of appearing in public view (not at home!) with uncovered hair divorce without a Kesubah–due to the gravity of how pritzusdik it is to allow other men to see her hair? Do they know that even a kalta (a basket) that does cover the hair, but does so improperly, also has the same consequence? Can they explain why wigs that make them look more glamorous than their own hair does are perfectly fine?!”
The entire reason for the head covering is to prevent men from noticing and being attracted to a married woman, which is a very grave sin. The wigs today do the very opposite and are making a massive Chillul Hashem.