Why do people link to Wikipedia pages as canonical references in articles/web posts even when better pages exist outside Wikipedia (and often without even reading the linked-to Wikipedia pages)?

I'll usually link to them for things I'm pretty familiar with or most people are just to make sure everyone is on the same page--to give background information.  If it's something widely debated or that few people know about, I'll try to link to something more solid, like a peer-reviewed paper. I think a lot of preference is given to wiki because, although it's subject to inaccuracies, it has a lot of people looking at it.  Sometimes the pages linked to are even more obscure, often hits in google are poorly thought out blogs and it's hard to determine the accountability.  Even trusted reporting sites like Wired can get things wrong (and like a game of telephone, reposts can get even worse).  It's just comforting to a lot of folks to imagine there are people maintaining wikipedia.

In addition to the answers already given: often, high quality content is managed by organizations that have very little understanding of how the Internet works. For instance, major news organizations, government agencies, or academic institutions. When you have the experience of linking to high quality content, only to have its address changed with no forwarding information, you tend to get irritated. This happens all the time on sites like those mentioned above. So maybe you tend to link to Wikipedia, which (1) has managed for over a decade to keep stuff in the same place and/or leave a redirect link when it's moved, and (2) tends to update its outgoing links, when possible, when other organizations screw up. The last section on this page points out a news organization making this boneheaded mistake -- one example of many: http://en.wikipedia.org/w/index.php?title=Wikipedia_talk%3AWikiProject_Oregon&oldid=508410474#How_to_repair_Portland_Tribune_links (Disclosure: Years ago I used to work for the Portland Tribune; it's a paper that has done a lot of good, but the Internet has never been its strong point. As I said, there are any number of other organizations that have made this same mistake. I'm only singling them out because it's the only example I know of an online reference for.)

Because many Wikipedia articles are "good enough."  A couple misspelled words, biased facts or uncited statements doesn't render it completely useless.  To be honest, most other sites are just as "bad" if not worse.  I've done alot of work on the Jack White article, and am shocked at how often I find wrong info in Rolling Stone, The Washington Post, The Toronto Star, and The Guardian. I still don't know the actual year the Third Man Records started, and I've read 1000s of words on the topic.   So many conflicting dates from different sources, and Jack White is a notorious fibber (which is exactly why we can't use first-person sources).  And BOOKS and BLOGS? You can forget it--they barely even try. If you want a true picture of ANY topic, you always need A LOT of sources.  But for one that's probably mostly right for a general idea of the topic, Wikipedia usually does the trick.