Remastering PS4 games to PS5, like what?

The PS5 is already backwards compatible with PS4 games. So why bother wasting time remastering so many PS4 games for PS5 when they instead could remaster older games NOT available on PS4 or PS5? There are tons of old games I would like to play on my PS5. But instead they choose to remaster newer games like Until Dawn, The Last of Us Part 2, Horizon Zero Dawn, Marvel's Spider-Man. Games that already are good enough as PS4 games.