Why do frats favor sororities before they know all?

I don’t understand what the hype is with old row plus KD? I’m in a “new row” sorority and it’s so fun and there are so many pretty girls but frats always just wanna hang with old row houses and the KD’s. Especially Fiji and ATO are obsessed with KD’s and I don’t even get it cause they aren’t even old row. Besides i don’t even understand what makes old row “top tier.” Like so many guys have told me theta’s are kinda dry and their socials weren’t that good but they still get the invite over us all the time. Like if we haven’t they won’t even schedule a social with us how will they know how fun we are?