Because Wikipedia is a virtual encyclopedia, the cost of creating an additional article is marginal—especially compared to the old print encyclopedias. In theory, Wikipedia could host an entry about nearly anything. But shouldn't a line be drawn somewhere?
This is one of the oldest philosophical debates on Wikipedia, and it has given rise to two of the best known opposing views held by Wikipedians: the Inclusionists, who prefer to retain substandard pages so they can be improved, and the Deletionist camp, which favors quality over quantity, and deleting low-value entries.
The middle ground—which is probably the consensus view—is called Mergism, which seeks to retain useful information (if not as standalone articles) and decide on a case-by-case basis. Because of this, Wikipedia's Articles for Deletion process can be highly unpredictable—and frustrating, or fun, depending on your persuasion.