I recently ran a game of DW and one question I got asked was why is complete success 10+ as from a probability perspective you are most likely to get somewhere in the 7-9 range and no outright success!

I explained that I thought it was because 7-9 is more interesting than 10+, its not a failure but success with a consequence. 

Was I right? Was this the rational behind the breakdown of success failure as it was? Kinda curious really!