why the bottom tier hate?

So I'm in an upper mid/lower top sorority depending on who you ask, and I cannot for the life of me understand why people are always putting the bottom tier sororities down and pitting them against each other. As people say all the time to defend them, a lot of AGDs and DGs are friends with each other, so I don't think they're the ones on this site spreading the hate. Even though some posts on here are most likely written by DPhiEs, they'll figure out soon enough why most of us in all tiers despise this site and tone it down, and this "let's make the bottom tier houses fight each other" mentality has been around since way before DPhiE got here, so I don't think they're the problem. SDT probably isn't the problem either since they are happy with their chapter, get a lot of the girls they want, and accept that they're different. So if the bottom tier houses aren't the majority of the people posting hateful crap, it must be people from mid and top tier houses. So why? Do y'all really feel soooooo threatened by these sororities that you'll do anything to keep them down? If they improve, is everyone else so insecure about your own chapters that y'all are afraid if they get better, your chapters will be the ones to take their place on the bottom? Like what ever happened for rooting for the underdog? I personally want all the bottom tier houses to improve and get better and not have to be bottom tier forever, and I have faith in my own sorority that we won't fall in the rankings