I live in Northwest Arkansas, and have found many revolutionary and war of 1812 buttons, and of course loads of civil war items.
I always attributed the earlier stuff to be from veterans who had eventually moved further West, and to the fact that good metal buttons were a premium when people were making their own clothes, and were likely kept and re-used in many cases.
Just my thoughts, but i do know my Grandparents, who were born around 1900, still saved buttons off of worn out clothing to reuse later.