I was wandering the same thing. One reason it could be that because the female lead lives through 4 gerations of emperors-- the grandfather, the father, the husband and the son-- so the director has to make her look old slowly. Wearing long hair make the queen and concubine look younger. Maybe they will pull their hair up later. Then add some grey. Chinese actresses never like makeup artists to draw wrinkles on their face. That will make them look...old. It's ok to toy with their hair, but not their faces. Hehe.