I've never forgotten to turn it on, but definitely forget to turn it off at times. Usually notice when I finish eating.
The reason why it gets left on is I usually am taking something out of the oven before I'm certain it's done, then an serving up a plate and forget to turn it off.
We were looking into remodeling our kitchen soon. Most places start at 70k-80k, and it just goes up from there. It's insane, we're no longer planning to remodel.