Why do people not like MOO?

I usually only use it for tiny things, like landscaping as many have said. Mostly of the time, the Alt key will suffice. I think the only time I use it a lot would be placing windows if the roof would normally get in the way. Since that doesn't affect gameplay, I'm usually fine. It can be so frustrating when it's used for immense amounts of clutter.
I've never left it switched on though. I used to get a lot of problems with routing in the early days of Sims 3 if it was left on. So I never really got into the habit and I'm glad I didn't.