The article states that the PS5 is responsible for significantly more gaming hours, so a large number of PS4 users are likely mainly using their device for streaming or similar. Hell, I still have my PS2 and 3 in my closet since they're my only dvd and blu ray players.
I have yet to buy a PS5 because there isn’t a game I want yet. Also, Sony tends to release improved consoles with lower price points and smaller footprints after a few years.
For some reason that doesn't surprise me. When I got a PS4 there were like at least 10 exclusives I wanted. This gen seems it's mostly remasters and remakes. So ignoring that Sony games come to PC now it doesn't even meet my criteria of number of exclusives to justify picking one up.