Brad Plumer at Wonkblog has a post on right to work laws which gets into their history.
If I remember my sociology professor in college had a take on the union shop and farm programs. The idea was that viewed broadly, the government delegated some of its sovereign powers to collective entities or defined groups, whether it was workers or tobacco farmers. If, after a campaign and a vote, a referendum, the majority of the people in the group voted "yes", the government gave the majority the right to impose rules on the minority.
Today we see this as an answer to the "free rider" problem, though I don't believe that terminology was in vogue in 1962.
Examples of this process would be labor unions, agricultural marketing agreements (for fruits and vegetables), agricultural promotion assessments, the old marketing quota problems for wheat, tobacco, peanuts, cotton, etc.