Because enough people don't mind being gouged

They're no longer conceptually different in the case of discs (though maybe for the cartridges Nintendo still uses). Inserting a disc into a ps4 for the first time often just triggers a download for all of the game data, rather than copying from disc. Add to the fact new releases are heavily patched these days which requires download. At least in the ps3 era launch titles were a fairly complete product.

Once Sony phases out support for the ps4, the console is rendered useless for playing anything that isn't already installed. Hence my copy of Bloodborne is staying on there. I know they'll probably release some "remaster" but I'm not keen on re-purchasing what I already own (there are gamers that do this... buying a game multiple times, even in the same console generation, it's crazy).