Wow, you seriously just cleared up a decades-old mystery for me. My mother used to save her receipts, and I mean to the point when she finally had to move out of her place and into a care home (in 2014), we were tossing out faded receipts from the 80s, 90s, etc. I wish I were joking. And it wasn't only shopping receipts, she kept all of her bills with the "paid" stamp on them (from back when people paid bills in person), etc. I asked her many times why she kept them and all she would say was, "because I might need them." Now, it makes sense.