My Dad saved stuff. All sorts of stuff. Not stuff like string or stamps, but stuff like nuts and bolts, old two by fours, chunks of metal, used spark plugs, wire, rope, cable, pipe, and, of course, every tool known to humankind. I have an old anvil/vise that was his. It weighs more than I do, and is solid iron decorated in rust and grease. It has seen probably 80 years of hard use, and is ready to go for another 80.
We used to say, apropos of Dad's penchant for keeping things, "He was raised during the depression." And that's true; he was 18 when Wall Street took the big one. We also said, "It's because of his upbringing." And that was true too. He came from a Kansas farming family that couldn't quite make a go of it.
Both those things, surely, will move a person toward saving and making do.
Today I started cleaning out my garage. Only one side, mind you. I who was raised amidst enough if not plenty, who am not a farmer and am not anywhere near a depression, have more stuff in the right side of my garage than my Dad ever did on his best day. In his best year. I have a set of delicate metal tubes that are extensions for my canoe seat -- except that I don't have that canoe any more. However, you never can tell when you might need a canoe-seat extension. I have enough tent pegs and tie downs for 16 and a fraction tents. I have three extra sets of automobile floor mats. I have enough towels, rags, and polishers to the polish the Eiffel Tower and still have enough to clean up the drips. After all, you never can tell.
So, I'm thinking that amassing piles of useless junk isn't a function of training or life experiences. It's genetic, pure and simple. I have inherited a junk gene. My first wife had a neat-freak gene.
If you are the partner of a neat freak, it's not their fault. If you're the partner of a junk junkie, it's not their fault either. Live and let live, and whatever you do, don't try to change them.