Why Is So Much Rice Grown in Paddy Fields?

70% of rice around the world is grown in paddy fields, that must mean that 30 % is grown in dry places. So why can't we just expond the use of the rice that grows happily in dry conditions and use that everywhere else? Smeter is trying to develop rice varieties which work all over the world. And with the right variety, we could grow it globally with with no paddy fields or virtually none.