God has given us over to our own debased minds to that we would come to Him, lovingly and willingly, and not forced.
There is no true love in forcing another to love you, so He sits back for a time to lets those who accept the calling to come to Him out of that love, respect, and honor Him for creating us to live.
The other aspect that some do not see is that satan is the prince of this world right now, and there are scriptures to prove it. Which is why there is so much suffering, pain, evil, and death in the world. If God was to come back now He would interfere with His own plan of waiting tell the time of the Gentiles is fulfilled.