confused about middle tier

I prefrenced at XO...
I won't specify but yeah they were my second choice and I went to what i guess you can call top tier.
However I'm a little confused as to why XO is comparable to AXO?
I thought AXO was really awkward and weird and I don't get why XO isn't the same as DZ? Honestly the girls i know that went Theta were unattractive and Pi Phis are not very classy so why are they upper mid?? Is it all based on partying?? Because if it was based of classiness/looks it would be different.

Please clarify or adjust the ranks because I do think these PCs have changed them.