Well, perhaps more primitive societies didn’t do it for a few reasons.
The Georgia frame buckle requires a fairly good bit of brass to make compared to common 18th century buckles for example, though there were some horse buckles then that were fairly robust. However, if one could afford to buy and keep a horse where the fancier buckles were used, they had the money to spend on more robust brass buckles.
It still amazes me how “delicate” looking the “double D” buckles used on the cartridge box supporting strap ends were in the 18th century and some of them were made for 3” wide straps in the mid 18th century.
However, there were some brass buckles that had a lot of brass in them from the 17th as well as early to mid 18” century, though they were often used as adjustment buckles on what must have been EXPENSIVE over the shoulder sword hangers.
The cost of brass was still much higher than iron throughout the 18th century and the early 19th century. No doubt part of the reason so many “delicate” looking buckles had Iron tongues. ( I sometimes marvel at the way they saved a tiny bit of money here and there on things. Sort of like going into an Ice Cream Parlour and eating a giant banana split to get the second one free and THEN ordering a DIET Coke to save on calories. Grin.) The other part of the reason was it was easier to form Iron into tongue shapes without cracking, like brass tongues MIGHT occasionally do.
Probably most of the Brass Buckles used here before the American Revolution were made in England from London and especially Birmingham, that was well known for the manufacture of “Brass Toys” ( that actually meant items such as buttons, buckles, sugar tongs, etc.) by the middle of the 18th century.
The other “problem” with the Georgia frame buckles may have been they required a double set of holes tor the two pyramid shaped tongues. They also required different shaped holes, sort of like flat rectangles with rounded sides. You can make such holes by punching two round holes on line and then cutting straight lines across the top edges and bottom edges of the holes, but that is a lot of work. So they probably would have wanted special punches made up to make those holes as they did for M1907 leather slings.
However, what must be the major reason not to use brass buckles like these in the 18th and early 19th century is a combination of the cost of brass and if you wanted a sturdy, inexpensive buckle, then it was made from Iron. Any Blacksmith could forge Iron buckles from scrap iron pieces he had on hand and he may not have had the “founder’s tools/equipment” to heat and pour brass, though gunsmiths usually did. Buckles with single tongues were what most ordered, so that's what they made.
I wish I knew the “relative cost” of iron to brass buckles in the 18th century and I just don’t know that. I get the feeling from original accounts that brass buckles cost anywhere from two to five times as much as iron buckles, but that is only a guess.
Gus