Microsoft Research is and has been doing some of the most interesting work in CS. Microsoft company proper however has a historic PR/cool-factor problem. Beyond that conjecture, this is basic experimentation.
My guess? They think Amazon is on the right path with the Echo and expect to interject themselves as a SAAS B2B layer between "hot young company" and "eager millennial consumer". It's also possible that they finally got around to watching those commercials of Katy Perry talking to Siri back before we realized that Siri is a useless bitch.
Mr Nadella predicted that speech would become as important as mice and keyboards as a way to deal with computers. “Human language is the new UI [user interface] layer,” he said. “Bots are the new apps. Digital assistants are like . . . the new browsers, and intelligence is infused into all your interactions.”
