Alex Bosworth writes:
In communities, a precept of personal motivation to work within a community is often governed by a two stage reward system. The two stage reward system works thusly: All new entrants into the community gain small but satisfying rewards for basic participation, but fanatics claim the larger rewards through elite competition.
This principle exists online and in real life. Many people play chess, and find it a stimulating and rewarding game. However to the masters of chess, motivations revolve around competitive ranking levels among other players. In massively multiplayer online games, the end game is very different than the casual game, because a certain class of player will commit vast amounts of time to play and game designers anticipate this by structuring the end game around an obsessive and competitive style of play.
Wikipedia, like most other communities, shares in this same principle.