Why are opinion articles often used as sources in Wikipedia entries?

Because they want to become popular online.

Anybody canupdate their thoughts, if the information is valid

Wikipedia can be edited by anyone at any time. This means that any information it contains at any particular time could be vandalism, a work in progress, or just plain wrong. However, because Wikipedia is a volunteer-run project, it cannot monitor every contribution all the time.

The opinions stated are derived from investigating reputable sources.

wiki is set up by the users , and the users arent accurate , thats why we got to reputable sites to get information , you know they get the information of specialist and confirm them , wiki depends on users who dont get paid and dont check the legitamicy .

UNKNOWN AND WHY IS this ques here? TIRH

Because man loves to have his ears tickled.    "What Is Truth'? 

And this has to do with Religion how?

Important political topics in Wikipedia are edited and locked by leftists. It is almost impossible for others to provide a different POV.

Actually anyone can edit a wikipedia article