Because we've enslaved a lesser group of sentient beings on Mars who are at this very moment, mining unobtanium for us.
Mars has a lot more quadrants to explore, lots of known unknowns to titillate and entice
Saturn is just a bunch of boring gas and crap.
Mars has water and could've had life. Its exciting on an emotional level that a gas giant could never be
Because Saturn is pweeety...and Mars is dry, red and boring.
They make educated guesses.
Well, they get some stuff right. I don't know enough to know any better.