Because Margaret Qualley has Tourettes and Hollywood is trying to hide it from us...thats all I got from the trailer.

@acontributor said:

I asked myself the same question. Why not just stay on Earth and live indoors? Even with a poisonous atmosphere it would still be a lot easier than building and moving everyone to a space station that orbits one of Jupiter's moons. Interstellar travel would also be a lot easier from Earth as home base.

This was the point the film was making, only more extreme. The film says, "Adapt or die." Even the scientist who was a "remainer" in the end gave up faith in biology to overcome. Humanity's lack of faith in biology led to irrational fear, and ultimately a poor decision.

@acontributor said:

IO was also a bad name for this movie since none of the movie takes place there. They should have called it The Last Woman On Earth or something that makes more sense. It's also more interesting. That's also not how Io is spelled. (Only the first letter should be capitalized.)

I can't tell if you are serious or joking, but IO is short for Input/Output. It could also alternatively be interpreted as On/Off (as in a binary decision). I thought it was a particularly lovely and poignant name.