When you have an understanding of what Wikipedia considers a reliable source, it makes perfect sense that Wikipedia itself is not a reliable source.
Wikipedia even very clearly admits that it's not a reliable source.
In schools across the country, some teachers tell their students that they shouldn't use Wikipedia as a source of information. Those teachers understand that not all of the information has been thoroughly verified.
What those teachers may not have considered is that while 100% of the content found on Wikipedia is not verified, much of the information is. Additionally, the reliable sources used to verify information is not only found at the bottom of the article, the reference itself is usually used as a citation in the text of the article.
In short, while the text in Wikipedia shouldn't be used as a reliable source, Wikipedia is a great source of references themselves. There are few places where students can find information on a topic as well as additional sources of information about that topic, all in one place.