Wikipedia consider as a Search engine and working as a non commercial domain and only offers information for Internet user.
and you know all non commercial domain find more priority for Google search engine side and next one thing is that Information based domain always rank better in search engine.
Wikipedia has earned its reputation as a “authority website” that is it does not spam nor it includes ads or affiliates.
It is looked upon as a credible source of information in Google’s eyes.
Reasons of this maybe,
-thousands of quality back links.
-most of their pages have a high Page-rank.
-Wikipedia uses lots of internal linking.
-highly searched keyword in anchor text
Hi,
Wikipedia offer true information about all the topics related to entertainment or other topics and produce backlinks for the site too in search engine.