Good point. Great question. We just look for the most “likely” places life might develop. Interestingly, though, there are lifeforms like the ones you describe here on Planet Earth!
You can find these lifeforms in Chile, specifically the Atacama desert. This place is burning hot and has had no significant rainfall in at least 250 years.
According to“While in the central valleys [of the Atacama desert], researchers found 70 species of microorganisms and further inland, the team made another shocking discovery.” What they found, 1 meter deep, was actual living bacteria.
Life does exist in extreme conditions sometimes on Earth. Why not elsewhere, like Mars for instance?
So far, however, we haven’t found any life or former evidence of life, anywhere except here on Earth.
It leads us to believe that if life is out there somewhere, the most likely place to find it would be in conditions that are similar to various climates and places on Earth.