The issue with an optional install is that the developer cannot really take advantage of them if they want to make a game run better, as many users will have to do with substandard games.
The main issue with the mandatory installs is that the developers can get lazy and just rely on the HDD to get them out of jail. I will forgive GTA, since there are basically no load times, but something like DMC, where it only decreases load times a little are more pointless







