Google's store is not the only way to get code onto Android phones (which is why I bought one, after rejecting iPhones).

Or, really, people build on this pile of sand because it's more valuable than not doing so. There is enough money to be had in the iOS ecosystem that even when you take into account the risk of being dinged for something stupid like this, it's still an expected net gain for many people to release an iOS app.

You missed the obvious reason:

Money.

Lots and lots of money.