What makes a "Lower Tier" sorority?

This is coming from someone who, admittedly, is in a sorority that most consider low-tier. Though I'm very confused as to why we have that designation. If App is supposed to be about pan-love and inclusivity why are we ranking at all? And what makes a sorority considered lower-tier? I've heard from other girls in different sororities that the only reason we're considered low tier is because we dont act like sorority girls... But what does that have to do with anything? I'm honestly sick of all the stereotypes, mind-games, and divisiveness associated with App State greek life. Why can't we just treat eachother like human beings?