It's much more difficult and expensive to get a human encased in a robot to Mars, than to just get the robot there, without the human. The attitude of the human is largely irrelevant (although if you are going to send a human, it seems advisable to not send a suicidal nutter).

There’s a difference between a suicidal nutter and someone who wants to do it because they’re thrill seeking and to make the history books as the first person on mars.

Also, there’s a huge qualitative difference between a human on Mars and a robot on Mars in terms of what it means for humans back on Earth. It’s an achievement people will take pride in, can help unify people, & inspires the imagination of the next generation in a way that robots won’t.