Its quite possible conditions for life that can overcome every possible hurdle to stellar colonization occur only once in a galaxy cluster or observable universe.

Consider all the things that had to go right just for our species to land on the moon.

Plus consider FTL is impossible due to causality violations.

Thus lets say a planet with life on it occurs even once per galactic cluster.

If we find life out on other planets its likely to be nothing more than bacteria.

Also consider, an interstellar capable civilization will likely iterate on constructing microblackholes as the optimal mass->energy conversion drives.