Valid argument, but we have a clear example that it is wrong. Humans. A lot of what we do is driven by internal value calculations and pleasure centers, so why aren't we all simply taking drugs and avoiding all this messy "doing things" business? Point is, if humans figured out a way of avoiding purely pressing the right buttons to enjoy themselves and actually being useful, so too will smart robots.
Most of us haven't actually experienced these powerful drugs. I wonder how many people could willingly pass it up if everyone had a significant experience with them.
(researcher) points at a junkie on the street: This person is in ecstasy. How would you like to feel like that forever?
(researcher) gets you comfortable and injects you professionally and painlessly with a controlled dose of heroin, leaves and returns in a few hours: How would you like to feel like that forever?
Outward appearance counts for a lot.