[Nexialist]

You can already produce fuel on Mars itself using the Sabatier Reaction with technology available today, you have to bring along a little hydrogen but that's not too big of a deal.

Refueling on the moon requires an (almost pointless) web of infrastructure that balloons the cost of a mission, and more importantly, increases the time to carry out the mission.

Each US administration has a habit of cancelling the more ambitious NASA/JPL projects of the previous one, so if we really want to go to mars, it has to be a mission doable in as short a time span as possible, such as proposed by Zubrin's Mars Direct plan.