Perhaps the best motivation for going to Mars is political. It is obvious that no single nation currently has either the will or the resources to do it alone, but a consortium of nations and space agencies could achieve it within 20 years.
“It is fatal for any body of workers to have forever hanging from the fringes of its skirts other bodies on a level just below its own; for that means continual pressure downward, additional difficulty to be overcome in the struggle to maintain reasonable rates of wages.”
“I've always been more afraid of being left alone or left out than of things that go bump in the night.”