Another big problem imo is also that you effectively lose ownership of your games. Inevitably, servers would be shut down and you wouldn't be able to download the games that you own. And that's if things go well. Some games could always just go away earlier as we've seen on other platforms. However, if you own the disk, then that's that, you can play the game forever.

On steam, the same problem could technically happen, but I trust Steam significantly more. It's very much in their best interest to keep growing their library of games and not stop supporting them. I still have games from 10+ years ago on it and I expect to keep them 10+ years from now.