@gnu2 The problem with this POV is that people need a way to know when a person is able to make important decisions for themself. Age works well, as long as we acknowledge specific (and detectable) exceptions (such a mental / emotional handicap) and ethical quandries (boss / subordinate, instructor / student, etc).

I consider "age of consent" to be a subset of legal majority, the age when one is presumed to have an adult mind and therefore one can sign contracts. (Again, specific exceptions should exist, such as mental / emotional handicap and influential /negotiation / market power ... where one party is in a controlling position relative to the other.)