Either saving on media costs (25GB disc instead of 100GB disc, maybe 1 disc instead of 2 if the game is too big), or even having more time to work on the game.
Developer makes sure the early stages are properly tested, send the disc for manufacturing including only those, use the manufacturing time to tweak/bugfix/optimize more stuff the rest of the game.
I haven’t heard of any disc game not being able to be played.
There's a number of games that don't come with the whole thing on disk/cart, usually including only the early stages and the rest needs to be downloaded.
The only question I have is what’s gonna happen as game discs are just becoming an access token to download the game and its updates.
That's a big concern. There's communities trying to document which games are complete on the media and can be played from start to end without updates (so no major game-breaking bugs or huge performance issues) like this one:
There's also the problem that they're clearly rushing this without much thought, they don't even have an answer to the obvious question of "what happens to people in regions not supported by PSN".
Not surprisingly that PSN page was edited earlier today, but there's a million screenshots floating around already, plus you can check the previous version in the Wayback Machine.
And even if it was clearly written on all places, it's still a "too bad you didn't read the fine print, now you're past the limit time for a refund, so either let Sony track you or lose access to the game" situation which is very shitty. There's also the fact that they sold the game to people in countries where is PSN is not available, which should not have happened if that requirement was going to be enforced in the future.
Not hard to see why people would get pissed and lose trust in the developer. I also think that players have been annoyed for a while with this type of requirement (not specifically in this game), and they are now getting a good outlet with a lot of publicity around to vent about it.
