I don't know where you get this from...just because we have not observed it directly? Based on everything we have learned so far about life here on Earth, it seems entirely reasonable to think that life would be very common throughout the universe.
Yes, it is true that you have plenty of life here, but you have it only on a very (and I mean very) thin layer on this floating rock. It seems a lot on the surface (pun intended), but it actually isn't.
(And, if you are willing to invoke some form of the anthropic principle, maybe a universe that can support even one instance of intelligent life is itself incredibly rare in some landscape?)
There may be a large number of life-hposting planets in the Universe, while still fitting current data that they are extremely rare as a fraction of, for example, the region of space reachable by humans, by floating space rocks, or perhaps even the Earth's light-cone.