And there are reason behind cutting hair in Buddhism!
When Buddha left the palace to seek enlightenment he severed his hair with a sword near a rock by the side of a river.
According to theravada sources, throwing his top knot into the air, and says if he is to be Buddha it will remain in the sky. It stays at a height of one league, until it is taken by Indra to Trayastrimsa heaven.
Whenever, a new monk is ordained, the first thing is cutting a bit of his hair by Lama. This is an auspicious symbol representing Buddha's first hair cutting.
As hair is often used a metaphor for human being’s illusion or ignorance, so called the ‘weeds of ignorance’, thus, cutting the hairs implies symbolically getting rid of ignorance.
The body and the mind should be kept clean in order to reach the final aim of true understanding. Thus cutting and shaving the hair represent a sort of determination to keep the body and the mind clean and then to attain enlightenment and save all beings.
This is the very reason why you see Buddhist high lamas, Rinpoche, Trulkus and monk with shaved or short hair with the exception of some high Lama since they need to maintain to follow linage traditions.