about dress codes per se. They were instituted at BYU during the post WWII era to combat the GIs returning and then again during the sixties to stop the hippies from changing the culture at BYU. They were a practical social response implemented by Ernie Wilkinson, not manna from heaven.
Idahoans are simply more ultra-conservative. This is not revelation but a means to control student populations because parents in those ultra socially conservative regions want it that way. Divinity has nothing to do with culture.