Why wouldn’t they? They serve shareholders, not you, the freeloader.
“Microsoft and Yahoo’s targeting service combines two crucial factors: their knowledge of users’ personal information and their ability to add cookies to browsers. Over the years, Internet users have given these companies their name when they signed up for free programs like the Microsoft suite of services known as Windows Live, which includes Hotmail. (Microsoft said it does not sell campaigns access to information users provide when they register for Office or other Microsoft products they’ve bought.)”