Which I would argue is only possible _because_ unions have mostly disintegrated. Scabs are a lot harder to hire, especially illegal immigrant scabs, if there's a union around to hold the company accountable.
I live in a new build neighborhood that's been under construction for the last 5 years or so. For the 24 houses in my circle I've seen countless workers come and go and 4 changeovers in foremen, all voluntarily. How would you possibly unionize such a setup?