Monopoly was originally designed to be a teaching tool. The idea was that it would demonstrate the evils of monopolies by making most of the players slowly descend in a spiral of poverty while one person becomes filthy rich.
One popular house rule is to place all taxes and fines into a pot in the middle of the board, which goes to whomever lands on the Free Parking space. This rule breaks the game to a certain extent, but in a way that makes the game more fun, as it gives the people who are behind a fighting chance to win.
It also demonstrates that one can succeed by skill and intelligence, but that blind luck works just as well.