[techphys_91]

Usually a reference indicates that an author believes something to be true, but won't explicitly state their reasons. It isn't just a statement of where information comes from, but a justification for trusting that information. If the reference is from a reputable source, then it indicates that this belief is justified. If an author believes something to be true because they read it on wikipedia, then that belief probably isn't justified, because the reliability of wikipedia content is mixed.

Good quality information on wikipedia often refers back to published sources, and at the very least an author should check that source and refer to it, rather than wikipedia itself.