Again, just because I think I was misinterpreted - it's not that you think they are ready for the death chat in their late 50's. It's that they may have, recently, gone through the experience of dealing with the legacy of someone who COULD have benefitted from the death chat.
I'll be very specific here - there is/was a specific 'depression' mindset. My parents, my husband's parents, many many people growing up early- to mid-century, grew up under its influence. Waste not, want not. Make do and mend. The instinct to save and, well, hoard! every little thing. Never, ever throw anything out, because you NEVER know when it might serve. I give my parents-in-law a lot of slack on this. This shaped their childhoods and their Nazi-occupied adolescences. Scrimp, keep, save, hoard.
The problem was, they then went through adulthood in a period of absolute prosperity. So they acquired, and acquired, and acquired, but never quite figured out how to divest. (And by acquired and acquired - I don't mean anything extreme, just that they lived a perfectly reasonably comfortable life). So the belongings piled up, but were never sorted or passed on, because...you never knew. Could come in handy.
Then they die. And their successors - my, and OP's, generation - come in and have to figure out what to do with all the accumulation that made them feel safe and settled. We're really the first generation that had to deal with this legacy of postwar too-much-stuff, and it wakes us up: we want to make sure our own kids don't have to do this for us. Hence the allergy to new stuff.
Again, not saying this is why OP's MIL cringes at the idea of a present, but just to put a finger on something many of us 50-somethings are feeling: for fuckssake, no more STUFF.