It's not tied to any demographic or age group - we all are collectors, in one fashion or another. From the time we started hanging onto our toys as youngsters and didn't want to let any of them go, through grade school, scouts, band, sports, high school, college, and throughout our adult lives until now, we have amassed a great many keepsakes.
Some of us start out rather innocently - just holding onto an item that means something to us. Others are more direct - hanging onto things because they may come in handy again some day (even broken appliances or parts to items). Others dabble in various types of collections - insects, books, collectible cars or dolls, trading cards, sports memorabilia, clothing, art, and more. Some keep broken furniture (their own plus "finds" at garage sales, the trash, flea markets, and auction) and similar items to recondition them and then sell them on eBay, Craigslist, or similar outlet - but somehow never really get to those projects.
We have tee-shirts, ticket stubs, programs, and photos (even before selfies) from all of those concerts we attended. Then we have the ticket stubs, caps, pennants, programs, and other souvenirs of ball games we have attended over the years - professional ones and those of our children and grandchildren.
This is why we have so much stuff and why many of us really can't move. We just have too much stuff to even think of going through it and deciding what to keep, what to donate, and what to toss. Many people are just thinking that someone else can worry about it after they are gone.
Over time, we have amassed such an amount of stuff that it may literally be impossible to set aside the time to judiciously sort through all of it and decide what is really worth keeping and what can be tossed or otherwise disposed of - yard sale, online sales, or donation.
Most of did not start out to create such a trove of articles from our past that actually would overwhelm us and take more space to store than we ever imagined. We have closets, basements, attics, garages, sheds, and now off-site storage facilities to keep and house all of our stuff. We likely don't even know a great deal of the stuff we are storing - having forgotten about it or possibly never intending to keep it forever anyway.
How we got to this point isn't really what matters. It's now that we are here, how do we deal with it? It's one thing to experience it personally, and it's quite another to witness it as an aging in place professional trying to advise a client on streamlining their lives and living space. No wonder this is difficult. There is just so much - so many memories, so many emotions and just so much stuff.
Ideally, we could all just agree to dump everything that we are hanging onto except for the essential memories, but then who is to say what this entails? Some people would say that all or most of it is important to retain. Others are already cutting back on what they retain.
Overall, amassing and hanging onto stuff is taking over the available space in our home. The more that we are willing and able to deal with this, the more comfortable and accessible our living spaces are going to be. Short of doing anything about the tremendous amount of materials we have hung onto over the years, we must help people adapt their living space to be safe and comfortable in spite of the extra burden of all the stuff that is present.