I love GIMP and I will die on that hill (yes, fully aware of the things it lacks, thank you). But for those who use Adobe products, from what I can tell, the answer is that they have no choice in the matter. Adobe is just that ubiquitous in that industry that you either use it or you don't work in that profession.
With Adobe dipping into AI stuff, I have an underlying fear they're going to become as ubiquitous in that domain as well, that people trying to compete with them just won't be able to. And then we will have the same problem in AI with Adobe as we have with Digital Image Editors and Adobe.