I don't know about that...
On my mom's part, she was a child of The Depression; she never grew up with a lot of material things. And, for a number of reasons, she left home as soon as she possibly could with little more than the clothes on her back. For her, I think, having nice things marked a kind of victory over her upbringing, and getting rid of items solely because they didn't physically fit in her new living place(s) has happened reluctantly at best. Her childhood also (I think) made her put emphasis on giving people things. So there's as much in her house as she can crowd in and she's not motivated to declutter or minimalize beyond what her kids guilt her into doing.
There also is, for her, some of the unfamiliarity that people now in their mid-80s have with the on-line world. She's got folders of stuff for whatever she does because electronic records are not preferable. So there's a volume of stuff that has to be managed and stored for her SS, pension, charge accounts, etc., and it will be harder (for me) to go through all that paper than to look at those records electronically. The best I can hope for is that she purges the paper that has no bearing on starting or ending those obligations.
Then there's me. I'm as much on-line with everything as I can be. Everything is backed up, almost always more than once. DW has access to my computer and to the password manager that gets her to all of our bank accounts, retirement funds, charge cards, etc. DW lived on her own for 20 years, so she's no stranger to running her own financial life, but she is not up-to-the-minute on our finances or all of the folders in my desk, partially because it's not an area of great interest and because she does not feel the need to be up-to-the-minute is imminent.
DW has been after me for a while to put the very basic stuff down on paper that she'll stuff in our safe-deposit box. For her, I'll do it. I have a handy-dandy form (that I downloaded from the Internet and -- gasp -- printed out) but I haven't filled it out because there's always something more pressing to do on any given day. It's not even procrastination, really; it's just suffering from insufficient priority and I sometimes hope nothing sudden happens to push it to the forefront when I can't do much about it.
It's also been several years since we reviewed our wills (as discussed in the Trusts thread). Yes, we should do it. But the logistics of it (both of us together, when the attorney is available, reviewing, etc.) make it so easy to push off the task till next week/month/whenever.
So IMHO it's not always refusal in the sense of being obstinate or in being clueless about it. For more than just our parents/grandparents, it's sometimes something we don't want to do for reasons we'd rather not address or it's lost in the hubbub of daily life, nevermind the effects of MYOB or dementia.