Sheer size alone doesn't equate to a guarantee of life. Especially when other factors (like timespan and the probability of life) come into play.
Even in a near-infinite universe, if the odds of life ever evolving are infinitesimally small, the end result can be the two variables counterbalancing each other so the final result is fairly close to 1 (or even lower). Until we know how probable the evolution of life is (and we currently have no realistic means of ever knowing that, because all of our knowledge is based on a single case study).
It's entirely possible that we shouldn't even exist.