Why does NASA even have to do this? Build some cool rockets and get us to mars.

Among other objectives, NASA's 1958 mission statement includes conducting aeronautical and space activities of the US for "the expansion of human knowledge of phenomena in the atmosphere and space".

So: atmospheric climate science directly falls under NASA's responsibilities.

https://en.wikipedia.org/wiki/National_Aeronautics_and_Space...

NASA launches and operates Earth-observing satellites for measuring the weather and climate.

Living on Mars long-term is a practical impossibility. Certainly much, much harder than living on even a climate-changed Earth.