Actually I was amazed on how liberal the child labor laws are in my state (Iowa). I did not realize a 14 year old could work in as many occupations as the state allows. A bigger restriction is the employers (many will not look at anyone under 16).
In all honesty I think it is wise and prudent to limit occupations for younger workers. I would not feel comfortable with my 14 year old handling industrial equipment or chemicals with some doofus 20 something explaining the process to her.
Also, her primary occupation right now is school. She already works very hard in her classes to get As. In addition she needs to start doing those extra things which increase her chances of getting scholarships down the line (as well as medical/vet/other professional school entry). Many of those things involve volunteering in hospitals etc (it is how the game is played).
I think waiting until your early 20s for marriage is a wise thing myself. My children have had a much better life full of more opportunities than I did when my parents got married in their teens. Also by delaying marriage until I completed my engineering degree, I feel I have accomplished my goals more readily than getting married in my teens.
Child labor laws were not instituted to protect children like most believe, they were implemented during the great depression along with minimum wage laws and the retirement system as a way to lower the unemployment numbers and free up jobs for others.
If everyone started working when they were young the 20 year old boss wouldn't be a doofus, he would be a seasoned veteran of his trade with over 10 years of experience.
As for marriage, you are correct that a 13 or 14 year old doesn't have a clue about who they should marry... but that was the reason that for all of human history until the last 80 years or so that parents arranged marriages for their children.