Well, because the Legislature voted for it, I suppose. Sometimes observing constitutional order and having only the response “take it up with the Legislature” is all the answer we get. In CA is age 18 or up to 19 if still a full time high school student
Like I posted it’s 21 only in ny and Mississippi. Ridiculous. You can vote join army at 18.
And you can sign a contract at age 18 in NY.