I Samuel 1:27,28 27 For this child I prayed; and the Lord hath given me my petition which I asked of him:
28 Therefore also I have lent him to the Lord; as long as he liveth he shall be lent to the Lord. And he worshipped the Lord there.
Was this a common practice for parents to leave their children in the temple as Hannah did when she dedicated Samuel by bringing him to the temple?
No. In fact, Israelites were commanded to redeem their firtborns by paying five shekels of silver.
Numbers 18:15 The first offspring of every womb, both human and animal, that is offered to the LORD is yours. But you must redeem every firstborn son and every firstborn male of unclean animals. 16When they are a month old, you must redeem them at the redemption price set at five shekels of silver, according to the sanctuary shekel, which weighs twenty gerahs.
Further, only sons of Levi were allowed to approach the tent of meeting.
21“I give to the Levites all the tithes in Israel as their inheritance in return for the work they do while serving at the tent of meeting. 22From now on the Israelites must not go near the tent of meeting, or they will bear the consequences of their sin and will die. 23It is the Levites who are to do the work at the tent of meeting and bear the responsibility for any offenses they commit against it. This is a lasting ordinance for the generations to come.
The case of Samuel was special. He was appointed as a prophet of the Lord. Generally speaking, Israelites were discouraged to minister in the holy services.
No, I think the account tells of Hannah's actions because they are radical, along with the fact that Samuel played a huge role in the history of Israel.