Actors Equity has something they don't like to get out. It's a right to work status.
This is my understanding of it.
This means you lose Actors Equity Right to Vote, Can not audition for an Equity show while you are inthat status at the Equity Auditions or come to the Equity Audiition Room. You can get a audition with an agent.
Let's face it... jobs are hard to come by and some actors (as a friend of mine in the show with many Actors Equity credits) adopted this status. He is playing a major supporting role and doesn't regret it one iota. In fact he played many leads/supporting leads in Non Union Tours and works steadily in the non union tours.
Actors want to work That is why they adopt this status. That is why you are seeing actors with Broadway credits in the non union tour.