Because Microsoft's goals are not directly aligned with fighting DMCA and similar legislation. It takes more than being technically savvy to fight legislation like this; actually, I would say being technically savvy but not experienced will leave you in an unfortunate spot because you'll see through all the copyright stuff but be unable to effectively fight it in court.
The question was rhetoric. They have huge legal departments all over the world. Copyright, licensing and patent contract law are among the most important areas for these companies.
