This is what I always heard from tradespeople I talked to.
The complaining sounds like it's all union bluster from bosses that never lost an opportunity to collect a fee (rent-seeking).
The COT always seemed like an arrangement to make labor sound like rocket surgery and take skim off the laborer.
I've saved some money buy doing a lot of work myself, and the actual trades I hired for keeping the job legal and insurable seemed to appreciate not having to jackhammer my basement floor and haul concrete, tear down drywall, drill holes, reinstall sinks and faucets, etc.
Plumbing and electrical always come to mind because mistakes can really f up your house, but if installers of flat surfaces (drywall, wood and tile floors, etc) think their industry is safe from people that have figured out how to cut things and stick them together, they are dreaming.
I don't think drywallers and flooring installers are under the umbrella of the College........ yet.
I'm sure someone, somewhere, is figuring out how to charge those folks licensing, training and regulation fees too.