Convincing people they maybe should get a computer worked much better if they saw that it might increase their productivity.
Techy folks all already had one back then, and Clippy was aimed at those still writing their correspondence on a typewriter. I have no doubt that switching to a computer was productive for them, even if it increased Microsoft sales in the process.
back in the day people needed to be convinced that they needed a computer and that they'd be able to figure it out.
if you see clippy on a showroom floor or on your friends pc, you might think "oh yeah, i suppose I could use a computer to do that!".