Jobs like this, with no skills are a dime a dozen, and are the types of jobs (like fast food) that are FIRST jobs, ones for young kids to start with and learn the work ethic and then move up and on to better jobs.
Someone sorting mail or flipping burgers does not rate getting $20/hr or more. That's just nonsense.
I'm not disagreeing with you in principle. However, the reality is, there are tens (hundreds?) of millions of Americans and billions of people worldwide with no real skills whatsoever. None. They're capable of nothing but jobs without a skill requirement. These people rightfully want to sleep, eat, buy stuff, and get healthcare just like everyone else. And yet, they either lack the circumstance, the ability, the willpower, or the mental acuity to grow beyond a job that requires no skills. I am not judging how they came to be in this situation, only remarking that this is their reality.
This is a fact. These people need to be able to survive their whole lives. They need to earn enough not to be a burden on the rest of us. How can this be accomplished? If we aren't willing to give them higher wages, and we're not willing to pay for them to get training to do something more meaningful, then this situation will never change.