You don't see the logic because you haven't been exposed to how the human mind matures.
The frontal lobes of the normal human brain, (Cortex) do not reach full maturity (growth) until the age of 22 to 23. The Cortex is the part of the brain that enables humans to make sound executive decisions.
Decisions like finding a suitable longterm mate, which career path to take, etc. In other words the 23 year old should be able to make some sound executive decisions about what they need as well as begin to figure out which paths are available to them will assist.
People should be legally protected from making executive decisions with long term negative consequences, such as prostituting themselves, when evidence has shown the human brain is insufficiently mature enough to make that category of decisions.
Time & Tide Changes Everything