It's far easier to move capital around to different industries. Not so easy to transfer your skills between them.
Frankly I'm glad GM is moving out now while the recession still hasn't hit.
But we do that all the time and with good reason. Blockbuster employees and coal miners for example. At some point the jobs no longer make sense.
Blockbuster disappeared because the technology it was built upon became obsolete. It also didn't require specialized labour skills - the employees just took their retail experience across the street.
This just seems like a different kind of situation to me. Automotive isn't going anywhere, GM just couldn't perform.
edit: I'm reading some other comments about drive trains and EVs & reduced manufacturing requirements due to it. That's interesting. Maybe I should read about this more