Stephen Hawking made headlines several weeks ago by suggesting that in 50 years, humanity will have settlements on the moon. That's essentially all he said. He didn't say we'd all be living on the moon in 50 years, which was how some media outlets reported it, but he did say that we'd have settlements on the moon within 50 years and settlements on Mars by 2100. Since it takes only 3 days to get to the moon and anywhere from 39 to 289 days to get to Mars depending on relative orbit (the average is 162 days), and since nobody has actually been to Mars yet, this would seem to be a reasonable assumption—that we'd colonize the moon before we start colonizing Mars.
So why is that there's a viable proposal to put colonists on Mars as soon as 2023, and no similar private-sector proposal to colonize the moon?
It's not as if we're talking about a new idea here. Sesame Street's Ernie sang (rather poignantly, for a muppet) about the plusses and minuses of living on the moon way back in 1978:
Some of the lack of interest may come from the fact that NASA has already developed plans for a lunar outpost that could be implemented within the next 10 years, but I think the answer comes from a deeper, more visceral place than that. Humans first visited the moon in 1969, when the average person's idea of cutting-edge technology was color television and the electric typewriter; if you're younger than your mid-forties, you have no memory of a world where people hadn't landed on the moon. But nobody has ever been to Mars, and you can barely see it from Earth without the aid of a telescope. It is, legitimately, a new frontier.
Still, the moon has a great deal to teach us. And while the idea of a lunar colony hasn't attracted the same degree of attention from investors as Mars One, putting humans on solid ground anywhere that isn't Earth—even if it's solid ground that we can look up at every night—would bring us closer to developing the kinds of sustainable offworld colonies that we may ultimately need.