What does it matter whether humans survive? If we're just animals with above-average intelligence and the ability to use tools, we're not ultimately more important than anything else in the universe, and we'll still amount to nothing in the end. So what does it matter whether the human species survives past this planet or past the solar system, etc?

This isn't a trite question, it's quite serious. Why do we assume that we are important enough that we need to survive as a species beyond earth? If humans are so destructive of their own environment, as many say, shouldn't we let that destructive habit end here, rather than spreading it to other worlds?

IIRC even with the more pessimistic model the Earth will be habitable for humans for at least a few centuries. Do you have a link to an article with a shorter timeline estimation?