Any other encyclopedia and any wiki-formatted knowledge store could be considered close competition. Wikipedia's in the business of providing high-level (and often low) level information, and there are tons of players in that space - just perhaps not as generalized and overreaching.

Wikipedia is a non-profit. They don't really make more money by having more people use the site

Which doesn't mean that it can't compete with other entities, just that it does so under a special set of rules. It's still in the best interest of Wikipedia to keep up traffic.