Hot Coffee wasn't able to be access in normal gameplay, but the fact you could use GameShark or Action Replay does make a difference. You're not gonna find anything spicy if you hacked Mario Kart Double Dash even if you try, where as someone underage could accidently find something they're not supposed in the case of GTA3. I agree that it's kind of a dumb decision, it's not anymore graphic than anything else in GTA, probably a little bit tame compared to everything else honestly. But the logic behind it actually is a little more reasonable than you're giving it credit for, and I'd actually be more inclined to agree with the ESRB on their decision if it was a game which wasn't already rated 17+.