Writing for a global, diverse, and interested readership, where they can't assume their readers (unlike their professors) already have a wealth of knowledge about the topic.
Interacting with a unique and active community that actually "talks back”, as they receive feedback on the content they have written—for example, other editors might provide literature suggestions, question the neutrality of what was written, or suggest other ways to improve the writing—meaning they must learn to accept revisions to their work.
Gaining a greater understanding of the difference between fact-based and persuasive writing style through Wikipedia's emphasis on verifiability and "no original research“ policy.
