I know AI is the big bogeyman right now (and it is especially pertinent to Adobe because the stuff that makes Photoshop and Premier and the like so good are the "AI" tools they have had... for the better part of a decade), but I think there is almost a zero chance that is a factor in this*

Because... the big companies care about that. If using Illustrator means that all of their content is being used to train models for their competitors? You can bet that MASSIVE amounts of money would be pumped into Inkscape and the like overnight. Almost as much money as they pump into the lawyers who will own Adobe by the end of the month. Same with Premier and Photoshop and all the other ones.

I DO expect Adobe to release something akin to a RAG based tool so that Company A can "save money" by feeding in all of their personal IP as training data to make a semi-personalized model. But there is zero chance that adobe is going ot risk aggregating that themselves.

*: Unless the secret is that Adobe wants to develop a service to detect the probability that art was used in the training of a model or even to implement some form of DRM to identify stolen art. Similar to what those god awful NFT models failed to do.