One's imagination tends to run wild when uncertainties about the unknown are mentioned. When we say "life" in the context of this article, that means simple microbial organisms, not little green men. I wonder if it is as some say that there are pockets where conditions are right for life to form in many places and therefore life is quite plentiful in simple forms in many environments. Complex life like what we have on Earth seems likely to be rare. There were so many conditions that had to be right from a moon that exerts a gravitational pull to maintain a molten core that generates an electromagnetic field to Jupiter acting as a natural shield absorbing comets, meteors etc. that could de-stabilize life.
I have no background in astrophysics, biology (exo or otherwise) and so my opinion is not worth anything, I saw an article explaining how automobile manufacturing grew in Detroit to the exclusion of other places. Cars were not invented in Michigan and there were places better suited to establishing factories and manufacturing. I wonder if this model applies to the development of life in some way. By that I mean, life has to develop in basic forms for other more exotic forms to develop. So on Earth, without the development of basic dominant forms of life, other forms would not have developed. I realize I may be "favoring" one form of life over others as more essential or necessary but with no examples of life in other environments, any number of theories could be viable.