. . . why is "Because I can" a sufficient motivation?
I guess you could restate "Not believing in society" in such numerous ways with enough leeway in the interpretation that it could be seen as in some way fundamental to the answer. I don't believe in society, I don't believe in consequences, I don't believe I can succeed, I don't believe in authority, I don't believe I will ever afford these trainers, I don't believe you will ever help me, I don't believe I can be stopped - all of these are a part of saying "I don't believe in society". Without that belief, society does not function effectively.
Lacking the belief in these things, simply being able to riot becomes motivation enough . . .
My brother, over Facebook today.
PS - I'd appreciate if y'all would leave a comment or three over at my bro's place when he finally posts the piece he's doing on the riots. The above is his sentiment, and I think it's a good one.
[Picture: A burnt-out car on Clarence road, Hackney, London, uploaded by Flickr user StolenGolem, via Wikipedia]