This only makes sense if your model is 'the labs are just breaking the rules all the time' as opposed to 'the labs have a legal theory of defense for the one aspect of the business which is legally questionable'. The question of whether doing something their terms of service explicitly say they will not do opens them up to civil liability is a much more certain one than anything they are doing around copyright. If they are doing this and anyone can prove it, they are going to be sued very hard, and it will be a pretty straightforward case.

(To put it another way: if the copyright arguments against training on data scraped from the internet fail, the big AI companies don't really have a business, so they are going to proceed on the basis that they do until someone forces the issue otherwise. They don't need to train on data from their customers, and that is an argument that is almost certain to fail in court. If you're carrying 100kg of cocaine in your car, speeding is a really dumb idea, but the analogous action here would be firing a machine gun into the air from the driver's seat)