1. They made themselves that way through rules. Did you know, for instance, that a contributor can not put original information in a wikipedia article? It has to cite a published source. This means that wikipedia is nothing more than a mirror site for other real journalists and authors. In other words, its search engine bait. It gets high page ranking, but only because it has good SEO.
2. Do I really need another reason? As if 1 weren't irrelevant enough! Another way Wikipedia is useless is that your teacher/professor will not accept it as a citation for your research! If its not good enough for them, is it good enough for you?
Group A: People living on the government dime
Group B: People being paid to post stuff on Wikipedia
Lets say you are a field expert and you post something on Wikipedia. Immediately 5,000 lazy people or people with an agenda are champing at the bit to destroy you. Which leads me to #4 - But before we go there, keep in mind that if you did take your time to make a meaningful article, you have to spend the next two days tracking down the twerps who deleted it after scanning it for ten seconds and arguing with them as to why it shouldn't be deleted.
4. People by nature prefer to tear others down than to build them up. After all, its much more fun to call people names online and rip them a new one than to actually read their article and make a meaningful contribution to it.
5. An information source is only as good as its editor. And in this case, your editors are people who don't have anything better to be doing. Most of us have a job and bills to pay. There is the off chance that this Wikipedia editor is using their free time to better the world. Maybe they get paid handsomely at their day job and have the time to ward off hordes of government bloodsuckers. More likely, you have a group of editors who live off government assistance, and therefore don't have to do any real work, or they are being paid by a group or individual to put things on wikipedia. Either way you get a biased group.
How are people who live off government entitlements biased? Well for one, they are biased against anyone wanting to cut government entitlements. For another, they are biased against any person or party who wants to cut government entitlements more than the next party (or biased for whatever party or person has promised them the most entitlement). After all, if you are living off of government entitlements chances are you are pretty poor because the government is so inefficient at converting taxes to entitlements that by the time it gets to you, a dollar only vaguely resembles a dollar. It looks a lot more like a dime.
In conclusion, if you want to really know something, then go to the source. It'll have had a real editor with a professional writer and you'll be able to quote it without sounding like a tool.
Me: "Oh thats interesting, where did you hear that?"
Me: "HA HA HA HA HA, and you believed it? HA HA HA HA!"