It used to be you could find a box of photos or keepsakes that you inherited to look back on how things were or when you were a kid. Now, most of that is stored on phones, and most parents probably don’t think to share or save them in a way to be passed down in the future.
Typically you’d want gigantic files. Lossless formats preserve detail that would otherwise be lost. I scan as .tiff and convert to .jxl. Smallest possible size while still lossless.