Since moms are nearly always women, they have the advantage in an argument of not having to use facts, using "feelings" and "you may have done what I wanted but didn't do it with the attitude I wanted (but never said, although you should have just known). Also, when beginning to lose an argument, they deftly change to a new argument or shortcoming of yours, without acknowledging the original argument was over (until she thinks of something new that appears to support her side).
BAM! Don't argue with your mom.