Banned from Normals?

Last night I played a normal game, with a champ Im very very bad at, because I was tired, was waiting for my sleeping pills to kick in and just wanted to try the champ. Riven. Now, I would never intentionaly feed. Not even in a Normal, but I did play very very bad game. Still, got reported and 2 weeks ban. But I thought normals was for practice only? So why is the ban so harsh?
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