Says who? Says all the major theistic religions. That's part of the scam, though, since God or the First Cause is characterized anthropocentrically to avoid spooking us with its necessary alienness and inhumanity. Religions have it both ways, with esoteric (subversive) and exoteric (reassuring and literalistic) traditions.

If God is imperfect, he might not be worth worshipping, in which case churches would lose their authority and flow of income. But Kazantzakis's "The Savious of God" explores the idea of a God that needs our help. This is the theme of Zoroastrianism, too.