We are finally, laboriously, expensively, able to climb out of Terra's gravity well.  So why travel all the way to Mars and jump down a different gravity well?  Once there, it's a complete reverse of economies-of-scale -- nothing welcoming or profitable and little that can be easily got at if it's not near the surface.  Nor can any condition be easily amended -- gravity, radiation, atmosphere, etc.  Might as well have stayed in space and created a manageable habitat with shirtsleeve conditions.