What's with all the mediocre jobs?

I was reading a chart that said in the United States over 60% of jobs pay less than 20 an hour. I am a delivery driver for Amazon and I'm surprised that there are jobs out there that take more skill and hard labor and they're only making one or two dollars more than me. Everything from firefighter, flight attendant, teacher, delivery driver, call center employee, and even jobs that require college degrees are paying crap? What's with this?

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