Better yet, why only in one part of the world (a small part at that).
Paul, to King Agrippa, in Acts 26:
"What I am saying is true and reasonable. The king is familiar with these things, and I can speak freely to him. I am convinced that none of this has escaped his notice, because it was not done in a corner" (vs. 25b-26, NIV).
It's the seed or yeast principle: start small and it will grow.