Because it's wonderful fun, not to mention immensely self-validating, to be able to look down your nose at someone. Our version of a pecking order, without the need for physical pecking. Just as well really. We'd have splitting headaches otherwise.
No, its not really fun at all, unless you're a sadist who enjoys seeing people get emotionally devastated day by day. In fact there are few things I enjoy more than taking people who think they're high up on some kind of social hierarchy down a peg or two, by whatever means is most entertaining to me.
So you indulge in precisely the same exercise as every single other person on the planet. I didn't say we all agreed on the pecking order.
Point is, we relish in - to use your words - "taking people... down a peg or two...". You consider yourself superior to them. It's just that "society" (or some elements of it) happens to give them a higher position. That societal order doesn't make the slightest bit of difference to the emotional meaning to you, which is built purely on your internal conception of the pecking order.
But that's actually true for everyone, even if they have a higher percentage of agreement with the conventional list, because there IS no actual, agreed list. That's why everyone thinks they can win at this game. And why we all keep playing it, in our own way. It's one of the core drivers of human behaviour. Not the only one, of course, but a strong core one.