Why do ancient men mostly have long hair, while modern men mostly have short hair?

In ancient times, parents who paid attention to figure, hair and skin were accepted by people from an early age. In modern times, due to the decline of traditional culture, western learning spread eastward and entered a fast-paced life, and short hair became the mainstream.

In addition: don't be influenced by time-travel drama. In many ancient dynasties, modern people's short hair was reserved for condemned prisoners or monks.