Because they look at things from an original perspective and do not follow rigid dogma.
I've picked this out of Martin Weller's new book 'The Digital Scholar'. (2011) This book is published under a Creative Commons licence that throws away the old concenpt of copyright and ownership, inviting people to do as they please with the content so long as he is attributed (indeed any of the other authors/academics he quotes himself). He is either on a mission, or playing at the edge of digital scholarship by inviting others in, expecting more than peer review for his thinking followed by publication years hence in an academic journal.
The stance I take, is that the outside, the novice, someone from a different discipline or culture, can, act in many ways to amerliorate knowledge, either as a catalyst for seeing things differently, or by seeing things differently themselves and in time being able to articulate this in a convincing manner. They don't have to wait for permission or acceptance, they just do it. So long as we can see (as you can online, say with a wiki) the trail of changes (editing, additions) others coming to this fluid material may draw their own conclusions (if a conclusion is now ever possibly given that a work offered online in this way is never complete).
I agree with Joyce and the thing that irritates me is the lack of incentive to be original in essays. Why must we find someone who's already said it just because we're lowly students?
It's infuriating when we have something unique to say but dare not mention it because we can't back it up so it'll be seen to be too subjective.