The ultimate goal isn't just to simulate the pleasure, but the experience.
One could just take heroin, but you could also just be in a simulation where you play a big game with a lot of people and you're also not at any risk of dying, so why would you skip the qualitative experience just for the reward, when there is no more risk to it?
Solving a problem is fun for the sake of it. The low IQ midwit pseudo intellectual will claim that the reason solving the problem is fun is because of the serotonin and dopamine, so you should just skip straight to that without the middle aspect of the experience. But the nuance of the experience is the point for the reward, and can't be replicated though only chemical reward. It can only be replicated through actual simulation.
So hopefully we will get put into an experience machine that simulates an incredibly large amount of different experiences, simulations, challenges, and games. Even things like pain and fear sometimes. Imagine a simulation of a medieval battle where you actually feel pain if you're stabbed by another person playing and actually feel fear because of it, but you do not actually die when your throat is cut. Such an experience is something that is desired, but isn't pleasurable.
