Well, before Earth becomes a paradise, living on other planets is fraught with consequences... We've littered and polluted here, and polished it with wars; I don't want to carry the same mess into space before we clean up after ourselves.
Other planets will have more resilience; after all, our footprint hasn't reached them yet, and everything is pristine. And besides, all our pollution is made up of the same elements from this universe, and we are also a part of it, which means that such a development of events is predetermined by it.