Not saying it's bad to keep old consoles...
I just know with me, I rarely kept them at first because I was pretty much perma-broke, so I
had to use them as trade-in toward the next gen if I wanted the new system at all. But that was also during the time before digital and download titles were even a thing. Physical copies FTW in that regard.
Now it's more an issue of that I really don't have enough outlets to support that many systems. With more systems now having a hard drive for storage, their tolerance toward things like power brownouts and sudden power loss is immediately called into question. Things like not having enough room to accommodate, or what to do when a controller starts wearing out and you can no longer find a compatible replacement. In this regard, BC became a huge selling point, because it immediately eased the pain for early adopters, and gave us something
to play while we either waited till we could afford new-gen games, and/or because the old games were still fun and worth playing.
Since the transition from cartridge to disc, it's without question that hardware reliability as a whole for consoles had degraded significantly (some moreso than others). So yea, if you have a fail-prone version of a console and it goes south when the manufacturer is no longer making anymore, or any way to play your favorites for the platform... what
can you do? At that point, you'd be pretty much held hostage to pay whatever ridiculous markup the likes of eBay charges.