I wasn't allowed to have long hair when I was a kid lmao, never really understood that.
I don't know when it happened that short hair = men hairstyle.
Knights, Vikings all had long hair back then. Heck even in Chinese culture (and maybe other asian cultures) cutting your hair was like the worst punishment you could possibly get, as filial relationships are extremely important in (at least) Chinese culture. Your hair was part of what your parents gave you, so cutting it would symbolize throwing away/ cutting off something your parents gave you.
(this was ofc true for both genders)