You don't need these fancy theories. The reasons are actually far simpler: Good luck being allowed into the skilled trade unions. My son decided after one year of college that computer programming was not, in fact, for him. He looked into the trades. They accepted applications ONE DAY PER YEAR. He also took a few community college classes thinking he could get into a medical tech field. He gave up because there were waiting lists for those classes. He eventually went into welding and is doing very well with it.