That depends on the scale of human society, doesn't it? Grow the population in the solar system enough and it becomes a smaller fraction of gross output than many trivial and frivolous things are today.

I'm arguing here that if non-interstellar space colonization is possible, interstellar colonization is a natural and feasible extension. You might argue that even colonization in the solar system will not occur, and I admit that's a defensible position.