Never mind the fact that this is the season with the most races in F1 history - 21 Grands Prix. It would actually be surprising if the second placed driver in the championship hadn't won a significant number of races himself.
Besides, it's also quite convenient to overlook the fact that Rosberg's approach for the last few races has been rather conservative as he didn't really need to win them, so that's less competition for Hamilton. The whole "reliability took away Lewis' championship" argument is flawed - we don't know what would have happened and how both of them would have raced if, for instance, Hamilton's engine hadn't failed in Malaysia.