Because, even if God (or whatever version of a higher power/powers you believe in) do exist, I doubt that they will have any direct influence in man’s free will, as was a gift from God/the God’s themselves.
If mankind truly wishes to posses freewill and choice, mankind must take responsibility and ownership over said choice. Praying for intervention when we were given the intimate gift of choice is contradictory. It would be going against the very allowance we were allowed.
And so, God/the Gods do not intervene. Because, ultimately, we were left in control. And in control we shall stay. As is what we wanted.