^ It just... is. Once you've seen a number of button-down collars, you notice that they're not all the same, that some look good and some look bad. Certainly subjective regarding which is which.
My lone LE OCBD has a great collar roll. Yours don't?Great collar roll from Eastvillage. Why don't my shirts do that? Do I need to bite the bullet and move up from LE OCBDs?
Fred Astaire would agree with the "jaunty quality" opinion, as he was into a softer more casual look (i.e. the brown suede shoes, etc.). He even wore BDs with a DB suit; probably a mistake. While it can be said the BD is probably the least dressy and most jaunty dress shirt collar, probably the tab collar is the most "uptight" looking, and the cutaway (Prince Charles' favorite) is the most formal. However, it is mostly a matter of personal taste and preferences and there are no rigid rules here.^ Yes, it's hard to explain. Or, rather, can't be explained. Of course it's a matter of opinion...but the settled body of opinion seems to hold that the roll gives the shirt a certain breezy or jaunty quality.
And there is also the matter of precedent. If you look at early pictures of button-down shirts (incl. old Apparel Arts drawings) you'll see that they always sport the roll. Brooks, the standard-bearer of the OCBD shirt, always had a significant roll to its collars. And so for at least 30-40 years, shirts without a roll have looked like a sort of cheap imitation of the original.
Here's a quote from Allan Flusser's "Clothes and the Man," I think he has said it all.This thread gives me the opportunity to ask something I have often wondered:Simply, Why is a collar roll so desirable on an OCBD?I know it may be a subjective question, but I am interested in responses.