Why Mars? Its just another gravity well. To paraphrase Heinlein; Once you reach high orbit you are halfway there. Halfway where? Anywhere.
And check this out.
There are a bunch of easy answers to the Mars questions, such as looking for life we know about, going near, practicing landing on another planet, making use of what we have near us, and so on.
I happen to greatly like Gregg Easterbook's writings, as a whole, to, but the space program is a spot where he is totally, completely, repetitively, blind. Alas.