The problem is that tens of millions of adult Americans work for less than a living wage.  I work in a production environment.  My job doesn't require a degree, but we have to do math, and we have to be focused.  There are no teenagers at my workplace.  Most of us are middle-aged, experienced people with a good work ethic.  When someone comes in who's not so bright, or has bad work habits, they get cycled out very quickly.  Yet most of us earn less than $12 per hour.  Our economy has devolved to the point where employers can have grownups for a teenager's wage.  It's nice for them, but not so good for the employees, or for society.

We could have a low teenage wage, or a low first 30-days on the job wage.  If it's really a job that requires no knowledge and no experience, then those employers will be okay with kids and high-turnover adults.  Employers who want grownups should pay a living wage.  A full-time worker should be able to rent an apartment.