Output quality immediately comes to mind, of course.
Models are converging, but they converge in bands, and frontier is frontier. I would not like to have any workflows in any area of my business where output is generated by an assortment of models from different providers. For trivial, mundane tasks that might be fine, but it certainly doesn't apply across the board.
The issue is that the legal system is retroactive, and information that is made public cannot be retracted. If a random company gets your sensitive data and disseminates it to the world, then sure, they will face legal repercussions, but the damage would have already been done to you.