The original Windows 3.x OS had a nice little teaching section on what a mouse was and how to click, double-click and drag. I used it a lot with students, but when Windows 95 came in, it wasn't there. Of course by then everyone would know what a mouse was and how to use it, wouldn't they?
Well, no, actually, they wouldn't.
There are still lots of adults who have never used a computer in their life before and they need simple exercises in how to do it. This has just saved me lots of time in trying to devise one.