I loved reading that OP. A very pragmatic and practical view on what we actually need and use. In a world of abundance and choice, it’s nice to hear stories, like your father’s, of the depression era generation making due with what they had available. Till the day he died, my grandfather never threw anything away and always made due with what he had.
I can't begin to feel how desperate times must have been in the depression. Like your folks, dad saved stuff that I thought was near worthless. I once asked him why all those old burned out electric motors were under his workbench in the basement. He'd saved every motor he had to replace on a electric furnace, or whatever. His answer to me? If times got hard again, all the copper wrapping in those motors would be valuable. He had stashes of gold coins, old jewelry, in case. Mom had stashes of canning jars in case food had to hoarded, and supplies of material and needles and thread.
Those people that came through the Great Depression had a kind of trauma that affected them the rest of their lives. Dad had his one pocket knife, so he never got another one. He considered it almost a sinful waste of money to have a duplicate. Just like he had that one old Colt .22 woodsman, he'd never get another gun because he had one that worked just fine.
Growing up in the prosperous post WW2 era, I can't begin to comprehend how horrible the Great Depression must have been.