IMO, the majority of younger people just don’t keep paper documents and file folders, and as much as possible they opt for a paperless option at all times, and scan and toss the outliers.
(I’m in my early 50s and I also have spent the last couple years getting as much as possible with my parent’s lives away from paper copies of bills and documents, especially as I either handle or assist them in handling everything from a different state.)
I think providing your grown kids with some sort of “table of contents” or list of things to help get them started is useful (just for knowing what sort of things to track) but I could see a lot of young people thinking that physical sort of system was no longer relevant to their current day to day life (while still seeing the usefulness of it for older people who do keep paper copies of everything).