This is complicated by PERM process for green cards. While many companies might not give damn about college degrees it is safe for them to advertise the job as if it requires college degrees. Just open the San Jose Mercury news and see all those job postings. There will be ads like "Want an individual with Masters Degree or Bachelors degree with 2 years of experience with courses in AI, Database and Web Programming".

There might be artificial factors requiring the factories to hire people with white collar education.