It is several reason why Bosch (not BMW) has encrypted their ECU's. One is to follow rules and regulations for emissions. Another is to make sure cars are not tampered with for safety. Third a lot of countries have taxes related to performance. So I am quite sure government policies has forced the industries to implement this.
There is an interesting thread about this over at the M3-forum:
http://f80.bimmerpost.com/forums/sho....php?t=1065967