Same here - Why would you region restrict a game and give up on sales?

It's usually to prevent consumers from one region buying it more cheaply in another region.

There may also be issues of asset rights, censorship and copyright involved.

Uh, what stops you from setting the same price in all regions?

If I had to guess, differences in currency value and return on investment in different markets, to get as much value out of each region as possible, while limiting the effect of trade between markets to drive prices down.

Note that we're talking about the iOS app store here, not physical goods... kinda hard to trade app store purchases between regions isn't it?