Answer:
The novitiate was essentially a probationary training period for anyone wishing to become a monk and during this time the tonsure was not appropriate.
The tonsure was only given once the novice became a professed monk and a full member of the religious community; at that time he made a will, had his hair cut in the Roman tonsure, took his vows and was welcomed with the kiss of peace. He also received the cowl, celebrated Mass and in some Orders spent three days in silence and solitude.