The thing is that we, on this little planet have very limited horizons and so there are constant struggles for minerals, land and wealth which all add up to 'power'. If you have mastered high speed inter stellar travel then you have access to all the land to live on you would need for a million years plus and all the mineral resources you would ever need and 'power' becomes a meaningless concept as there are no finite resources to control. The only reason to then travel the universe and visit other species is to simply reach out to other living beings. We look at the universe in the terms of our own little prison and treat 'aliens' as if they had that same blinkered, limited mentality. To a species who could visit us we aren't of any interest except as fellow creatures of the universe.
Think of this - A good large super nova will generate several times the mass of the Earth in Gold alone not to mention Platinum, Silver etc. and there are dead stars everywhere that are reckoned to be solid diamond. In those terms gold and diamonds become so common as to be only useful for industry and cease to have the values that we place on them because they are rare on our planet, well at least on the surface, as the core of the planet contains heavy metals in the millions of tons.