Edit: for Adobe, it may have coincided with significantly cutting back their Marketing/Communications department, which had a huge staff of really great artists in the 90's. I believe this became viewed as an extravagance to have a stable of really talented and creative artists and designers on staff when you can hire this stuff out and get "reasonable" results.
[1] example: https://www.yumpu.com/en/document/view/33241791/adobe-annual...