An interesting observation OP.
If I may proffer my theory as to why, it is because finally, people are realising that the acquisition of material shiny stuff neither makes one a better or happier person.
That in fact, becoming a better and happier person comes from within and is generally directly proportional to age and experience. Self awareness, empathy and other such attributes being the main drivers, rather than the ‘more stuff’ sh1t.
Additionally, all the various ‘standards’ now effectively mean that someone else’s unwanted ( because of the realisation they are neither happier or better,despite having purchased it new) stuff might not work with the stuff they already have.
And/or, it’s not worth as much as they thought it might have been but still ask top money.
Many more possible theories are springing to mind as I type, but I feel my first intuitive guess is pretty much on the money. 😀