Today a sufficiently large financial incentive is woefully lacking (and it always has been), which explains why nearly 40 years have passed since anyone traveled beyond Earth orbit.
From the Popular Science article:
If the Space Settlement Institute - which lobbies for private industry to develop land on other planets - has its way, new laws will allows space colonists to stake moon claims and start a colony.
Alan Wasser, the Space Settlement Institute's chairman, says that a private company should build a "spaceline," similar to an airline, between the Earth and moon. And because a corporation is not a nation, the [national sovereignty prohibition of the] Outer Space Treaty would not apply....
Wasser says that land ownership - and the promise of profits based on it - is a necessary incentive to invest in space settlement. He is lobbying for legislation that would commit the U.S. government to honor future moon claims.
The legislation proposed by the Institute is the Space Settlement Prize Act, which would "...create, at no cost to taxpayers, a multi-billion dollar incentive for private companies to finance and build permanent settlements on the Moon and/or Mars."
Interestingly, Stephen E. Doyle, another space expert quoted in the Popular Science article, thinks the Antarctic Treaty should be used as a template for lunar development. We strongly disagree. In the opinion of the Space Settlement Institute, it would be a terrible disaster for the future of mankind if the Lunar government were to be modeled after Antarctica.