PS2 had full PS1 backwards compatability. PS3 at launch had full PS1 and PS2 backwards compatability. Later models removed PS2 functionality but PS1 remained. PS Vita despite lacking a UMD drive had a large catalog of PSP games available. Both PSP and Vita had a massive amount of PS1 support.Has Sony ever cared about backward compatibility though?
All their efforts on that so far has been half assed.
I'm sure the only reason PS4 games are going to be fully backward compatible on PS5 is because modern architecture of PS4 and PS5 made that extremely trivial.
PS4 is the outlier and it fucking sucks. They need to recify it with PS5.