If all life on Earth came from the "Primordial Soup" that was created by comets and asteroids impacting a cooling Earth, then we must assume that all planets with similar atmospheres and with available water must certainly contain life. The elements that exist on comets and asteroids would exist everywhere in the universe at the same time Earth was being "seeded" with the stuff of life. Life on all those countless trillions of planets inhabiting those trillions of galaxies, which have had about the same amount of time to mature to roughly the point humans have. There should be countless numbers of individuals and mature societies out there. Why can't we find one?
Finding one would involve seeing evidence of organic development in the atmosphere's of these planets. We have the capability to see that now using light filters and techniques for planet discovery and we have discovered a great many planets within the confines of our own galaxy.