He's pointing out the stupidity of implementing that system in a single player game, where you don't have to have the same, unmodded version to play. I can download a trainer and give myself all those nice items for free. So, if I feel like cheating, I can use a trainer, mod or even a crack and give myself anything I want without the need to pay, whether in real-world or in-game currency.

Now, Blizzard isn't stupid and I'm sure they're aware of this and will go to great lengths to make it impossible, or at least unbelievably hard.