In Hinduism,the Hindus consider the children of the family not to be egoistic in nature but be humble,devoted and submitted to nature.So they need them to give up their adornment and vanity in humiliation. The Hair on the head is treated as an adornment and as a symbol of pride.Thus by shaving off the hair they submit completely,representing a real sacrifice of beauty and get closer.It is an act of humility and a small step taken to realize without any arrogance or negative thoughts in mind.