Pac-Man, I don’t know how old you are or what you have experienced but your knowledge is lacking. IT is NOT halacha by any means. If it were then the likes of the greatest Rabbonim such as Reb Moshe Feinstein, Rav Avrohom Pam, Reb Yaakov, the Lubavitcher Rebbe, etc. would insist that this “halacha” be followed or they would not be mesader kedushin for the couple. OK is that enough for you? It is a minhag/custom/shita whatever you want to call it according to where you come from, which group you belong to etc.
Many of us “married” women here on the CR did NOT cover our hair till the next morning according to our own customs and guidance from our own Rabbonim.