If you had shit to do, Clippy was the digital equivalent of some annoying pest of a person throwing out random numbers when you're trying to count cash.

If that's not enough, he specifically creeped women out according to that article:

Generally, Atteberry’s character tested well in focus groups—the best of any assistant in some cases. Yet its massive eyes could be buggy. Some women in the cohorts deemed Clippy a man, and the constant male gaze creepy. “There were comments about how Clippy was leering,” says Roz Ho, who worked in product planning for the PowerPoint team then. When Ho raised that concern, she says the men in the room—everyone else, basically—couldn’t process it. “It really wasn’t about, like, these guys were bad guys, or anything. It was just they had a hard time picturing that feedback.”