The utility function only specifies the terminal values. If the utility function is difficult to maximize, then the agent will have to create a complex system of instrumental values. From the inside, terminal values and instrumental values feel pretty similar.

In particular, for a human agent, achieving a difficult goal is likely to involve navigating a dynamic social environment. There will therefore be instrumental social goals which act as stepping-stones to the terminal goal. For neurotypicals, this kind of challenge will seem natural and interesting. For those non-neurotypicals who have trouble socialising, working around this limitation becomes an additional sub-goal.

This isn't just theoretical - I'm describing my own experience since choosing to apply instrumental rationality to a goal system in which one value comes out dominating (for me this turns out to be Friendly AI).