Actually, maybe I know the answer, but can't put it into words or don't remember.
Why do the majority of english riders use snaffles? I know what a snaffle is for and how it works and all that, I just can't explain why when we ride english it is customary to use a snaffle. I, myself, use a low port Kimberwicke (with which I do not direct rein), so that's probably why I can't think of what I need...cuz I don't use a snaffle! LOL
I can understand why you would need la lot of manual lateral control in dressage and jumping, but why a snaffle even just on the flat? Is it just because there's no real reason to go to anything more advanced? Tradition or historical reason? "Just cuz"?
(the reason I'm a bit muddled...besides the fact that it's 5am...is that when I used to show, people would have their horses in western classes in curbs but then switch to a snaffle for english. Why would you make a change like that...why not just use an english curb?)