Concept behind is that if a Extinction Level Event (such a big meteorite impacting on Earth) will cause life extinction on Earth, mankind as a race will continue exist into colonies. This hypothesis assumes that colonies are numerically large enough to avoid extinction by simple low natality rate. Further that they have to be independent from Earth in term of supplies. Even if this goal is remote the initial effort is worth to eventually reach it. The possible options are terrra-forming , i.e. change the planet atmosphere/soil to make it similar to earth or create artificial habitats who could survive by exploiting planet resources
Most of the planet in the solar systems are not habitable. Terra-forming is not a viable option since it would take centuries if not more. Self-containing habitat might be unable to be self-sustainable and a minor issue could put colony survival in jeopardy
There is a push to continue space exploration. Human colonies are the logical step forward in this process.
We should resume deep space exploration 50 years after initial Apollo missions. It
Rejecting the premises
Technology can not allow a self-sustaining environment nor terra'forming