CLaPorte, I'm not sure about anyone else, but it may be nothing more than force of habit. I really prefer loose rings and I ride a lot of colts, so for me, it's a needed safety feature but others might not have that problem. I even keep a chin strap on my full cheek LOL. I know it serves no purpose there but the bridle looks incomplete without it.
OP, the only thing I could nit-pick on is that you don't need a curb "chain" on a snaffle bit. I normally keep a full leather strap on all of mine similar to this
You can buy a length of saddle string at the tack store for less than $5 and make 4 or 5 of them by tying them yourself.