Reason 1: Generative Design is a horrible basis for building UIs.
GD requires a well understood model of how the design needs to operate and be built (ie, physics + specifications + machine tool kinematics). We don't have a physics of UI design. GD makes weird, ugly stuff.
Reason 2: Do you not remember how awful Clippy was?
See: https://en.wikipedia.org/wiki/Office_Assistant
TLDR Extract: The program was widely reviled among users as intrusive and annoying,[22][23] and was criticized even within Microsoft... Smithsonian Magazine called Clippit "one of the worst software design blunders in the annals of computing".
Reason 3: Also brought to you by Microsoft: the UI Hell of Adaptive Menus in Office 2000.
See: https://blogs.msdn.microsoft.com/jensenh/2005/10/10/combatin...
TLDR Extract: Adaptive Menus were not successful. In my opinion, they actually add complexity to the interface...Auto-customization, unless it does a perfect job, is usually worse than no customization at all.