I surely do not. You?
Atheist have a problem with morality in general and 'goodness' in this particular case. In the first case, there is no amount of reasoning that they can do to lead them to conclued that should not be amoral. Pragmatism, yes, but reasoning no.
As far as being 'good', how does one know what 'good' is? Atheist have no fixed, i.e. absolute, standard by which to judge their actions. Everything becomes relative and 'good' loses its meaning.
So, to answer the question; 'Why Believe in a God? Just be Good', I would say "Because without God, there is no 'good'."