The analogy doesn't hold. The technology, the ship, was already there. All one needed was the testicular fortitude (and money for support) to explore.
That is not the case with colonizing Mars. The technology wasn't there so we turned our attention to research at the ISS and building an advanced satellite network (both were very practical to human life). Colonization of the moon, let alone Mars, wasn't. Despite that, we have explored Mars with the technology we do have.
However, there is only so much one can do with the current technological platform (Newtonian propulsion). If we are going to have transportation which can supply colonization, we are going to need another form of propulsion (space-time warping perhaps). One could argue that we might/probably have such technology setting out in the desert waiting to be used. And there lies a big problem. For the last 40 years, our best and brightest minds have been working with the best materials, best computers, unlimited black budgets, etc. to develop such technologies in secret for defense. If they were successful, and they probably have been, revealing such technology would be a national security situation.
Anyways, point being, the analogy doesn't hold.