[UGAalum94]

I think it's a very regional thing. Among a certain type of southern guy, who isn't really nerdy despite what you're imagining, what we're saying is completely true.

It's not that they give it a lot of thought; it's just that they buy khakis instead of jeans and pretty much only wear t-shirts as undershirts. And this type of guy tends to be overrepresented in "good" fraternity chapters in the south.
(Hunter/fisherman types probably still buy jeans, but they wouldn't wear them too many places socially in adulthood.)

If you want to be in the chapters that are made up of these kind of guys, it's in your best interest to seem to be one of them.

In a different region, like the Southwest, the same type of guys probably wears jeans a lot; these things are going to vary a lot by climate and common activities.

ETA: I want to add that other chapters on SEC campuses tend to follow suit in their expectations, even if it's primarily made up of guys from the suburbs who grew up wearing cargo shorts and graphic t-shirts in high school. I'm basing this on my dad, my brother and conversations with former students, as well as my experience as an undergraduate, so my indirect observation window is a 50 year span on multiple SEC campuses. Sure, it may not be this way everywhere, but consider that a guy rushing in khakis and a polo is probably okay most places so no harm is done, but a guy rushing in cargo shorts and a T-shirt is probably limiting himself in some regions.