we've been hearing that 10-20 million number for how many decades now?

I believe the biggest problem with cdl drivers licensing is the truck driver training schools. They are pushing people through that have no business driving a truck. As long as the schools get paid for each person that the school gets financial assistance for, they'll pass them all.
I used to train drivers at my last job to operate a Ready Mix Concrete truck, I quit training because they were straight out of schools, and had no business in a truck.

A better question is how are they getting their CDL!!! LE cant tll someone they cant drive just because. You should know that

trucking schools are subsidized. few weeks ago someone in florida got busted for taking bribes to pass out CDLs