Don't blame BMW, blame drivers across the world who buy them because of the badge, not because they're bloody good cars. Most people have no idea how FWD differs from RWD, so why spend the extra developing a chassis that can take it if no-one cares?
To be fair, they've said that they'll only go FWD on the cheapy 1/2 series so we as enthusiasts shouldn't notice a difference. It's not ideal though, granted.