BMW, Michelin and others are all hiring now"
What you say is true, but most of those manufacturing jobs in Upstate SC are through hiring halls, not direct hires with the companies. $18 a hour starting is not great, but the slots do have some benefits. Now if you have a STEM degree, you can make a good living.
By hiring Halls do you mean temp agencies?
Where we live in Kentucky the Japanese owned plants hire through the temp agencies for what amounts to permanent help. The jobs can convert into permanent hires directly by the company. That occurred with a former brother-in-law.
I believe that this has come to be primarily because of government regulations. Workers that come via temp agencies can be cut loose a whole lot easier if they are not suitable.