I’ve never read the story but you can say that forcing her to cut her hair makes her “fit in” with the other people more and takes away from her original culture since she doesn’t physically have anything left to show about her true culture. she might try to start hiding her culture now because people are making her think that she needs to. in the future, she might make her kids cut their hair too and they might make their kids cut their hair etc. etc. which then makes the tradition of long hair eventually fade away.
They wanted to keep trade with china open. :)
