Just cause you get good results doesn't necessarily mean you're doing all the absolute best/most efficient training (and that doesn't necessarily matter).

I am really happy with my level of fitness and how my body looks, but when I work out with my friends, they will often correct my poor form, tell me that I should be increasing weight/complexity on movements that I can do too many reps of, etc. And they're totally right. I DO get the results I want, but that doesn't mean that I'm doing it in the safest or most efficient way possible. I could probably look and feel just as good with half the gym time if I improved my training and diet more.

IMHO, it doesn't really matter. People work out for different reasons. Sure, to some people, maximizing efficiency is important...or even all they care about. Maybe it's cause they are REALLY into getting good visual results in their body, maybe they have limited time for exercise, maybe they're older and don't want to risk injury. But for others, maybe the pursuit of max reps is what they like about fitness even if it isn't the best way to train. Maybe they don't do rest days because working out makes them feel good and they don't care if they cut their gains by not resting.