Of course it is an evolutionary spandrel, but we don't necessarily need to choose our goals to have the same ones as those of the evolution machine.

But I think the important part is that there is a very fine line of unhappiness with which humans can still be effectively working on goals. Even a minor, unnoticed, undiagnosed, and generally invisible depression can easily make people significantly less motivated to work on anything. If you choose any goal, say, colonizing the galaxy, you probably need at the very least almost happy people to work effectively on it. You need the kind of people who can joke and share a laugh while working, and feel content after a days work. If you have people who are constantly in a fuck-everything Office Space type of mood, they will not really achieve much.