It follows that factory work nowadays requires more technical skill than in olden times. Same with the military. You need at least a GED to serve in the US armed forces now. It’s not like the Civil War where you take the boy off the farm and hand him a musket.
Any monkey can get a GED. And with the level of factory automation today, any monkey can press a button to keep the production lots moving. Ergo, factory work (of almost any kind) will continue to pay low, as it should.