You don't need verifiable facts to know that retail and warehouse workers are wage slaves. Thats why unions are needed. Need a verifiable fact? Try living on $10/hr and tell me how that works out for you.
Not really. Everyone else who worked their longer, or had more experience elsewhere, got paid more, typically with a different job title.
Another job that was more uniform was in a factory, where I was making roughly $12 / hour. Not only was it unskilled labor, but those jobs were slowly disappearing as lines were being replaced with fully automated systems that only needed a third, at most, of the people to run them. Any effort to raise wages or unionize would merely ensure that the remaining lines were replaced sooner rather than later.
Therein lies the problem with trying to "solve" unskilled work. It's easier to automate, and there's more people capable of doing it. Given that often means that supply exceeds demand, wages are inevitably going to stay low, or the jobs will simply evaporate.
What's wrong with providing low wage entry level jobs for young people? It gives them experience. Rising wages would incentivize employees to stay in low-skill jobs for longer instead of moving to higher-skill-higher-pay jobs and letting other young people get those low skill jobs.