The end of puberty is variable and for most people, it happens much too young to be rational to consider them as an adult who is able to make more informed decisions. Puberty typically happens between the ages of 10 and 15 and I don't believe a person of that age should be expected to make choices like marriage, voting, driving, or owning property.
Currently, the age of majority is 18 or 21, depending on the legal circumstance. While people must be 18 to sign legal contracts, they have to be 21 to drink or inherit property. This is still far too young because too many accidents occur as a result of errors of judgment during this age. The age of majority should be raised, not lowered.