They might live in their generation ships, never feeling the need to set foot (or alien pedal equivalent) on a planetary surface. Most models of galactic colonization have been based on an analogy: the colonization of America by Europeans or of the Pacific islands by Polynesians. Perhaps a better analogy for colonization would be life’s migration from water to land. Just as fish don’t meet fowl perhaps ETCs won’t meet us. Perhaps they colonize space, but they don’t bother to colonize our particular piece of real estate; other places are more attractive to them.
