is not to compute its result, it is to show how much we do/don't know.
We're slowly, or quickly depending on your outlook, filling in the gaps. We now have enough data on extrasolar planets to do statistical extrapolations.
In the next decade or two, we will have telescopes nearly large enough to do spectroscopic analysis of the atmosphere of nearby extrasolar planets. In particular we will be able to see if they have significant dioxygen, which can only happen as a result of life as far as we know. That will remove another unknown value.
Advances in neurology and evolutionary biology will begin to highlight how likely it is for intelligence to evolve.