I used to agree with you and still do in a way since I have quite negative attitude towards fat people. However I now realize that while calories in - calories out applies to everyone we're still different especially in the way we experience hunger.

I'm thin and fit myself but I eat like shit. What differentiates me from fat people however is that I only eat about 3000kcal of shit and then I'm full and it may take quite a while before I eat again but I also go to gym and mountain biking and stuff so I use all the calories too instead of storing them as fat. I also sometimes simply just skip dinner altogether because I don't feel like eating. I'm just lucky that I can still function just fine even with an empty stomach and I don't experience aggressive sense of hunger like some other people do. Also I hate cooking and eating. Takes too much time.

My theory for why this is is that my body is just better at switching from carbonhydrates to burning fat (converting it into glucose) and thus I don't experience the drop in blood sugar levels the way some other people do to whom it takes a while for this process to kick in so they crash hard after all the carbs are used up.