If you plug values in drakes equations ou can make anything comes out. But historically with any like real numbers you get many civilizations right up until you state how long each civilization lasts. This is why Great Filters are such an important topic of discussion.
Try a calculator [1] and puch in your pessimistic and see what chances you actually get. It is really hard to get 10^20 without just getting 0, and we know the chances are higher than 0.
Well sorry, for that. Get a piece of paper and try it. The drake equation isn't too hard. It is just a bunch of probabilities multiplied by an amount of stars. You can even add your own terms if you don't like the one you have, but generally doing this takes yo further from the science...
Anyway, Here is a simple description I snagged from google search [1]:
> The Drake Equation is:
> N = R * fp * ne * fl * fi * fc * L
>
> where:
> N = The number of broadcasting civilizations.
> R = Average rate of formation of suitable stars (stars/year) in the Milky Way galaxy
> fp = Fraction of stars that form planets
> ne = Average number of habitable planets per star
> fl = Fraction of habitable planets (ne) where life emerges
> fi = Fraction of habitable planets with life where intelligent evolves
> fc = Fraction of planets with intelligent life capable of interstellar communication
> L = Years a civilization remains detectable
Now grab a pen and cocktail and make the math do whatever you want. I think that is you stick to realistic numbers you will get reasonably high values. But we might just disagree there.
My post had the formatting screwed up, but you didn't even try to show your work. You are just presuming what you think or want to be true without putting even the theoretical work into it.
Try a calculator [1] and puch in your pessimistic and see what chances you actually get. It is really hard to get 10^20 without just getting 0, and we know the chances are higher than 0.
1 - http://www.bbc.com/future/story/20120821-how-many-alien-worl...