Wouldn't surprise me if it was a contractual obligation from Microsoft. In the past they were extremely aggressive in offering incentives and juicy licence terms for companies that would help push Silverlight.
If you want to prevent your movie from appearing on the pirate bay in a DRM free format you have to make it so that nobody in the entire world is capable of recording the stream.
Even if you make sure the stream remains encrypted all the way from the server to the monitor, at some point it has to be decrypted in order to play. You only need one guy with the skills to take his monitor apart and modify it to feed the input into the actual OLEDs into another device. Once that happens it's game over.
The only way to really win would be prevent consumer playback devices from actually playing DRM Free content at all and insist that all content is signed. In essence force every consumer who wants to pirate to make a hardware modification.
This just points to the fact that software is notoriously difficult to keep safe via DRM, and that people _want_ the content, just not at the price point that large publishers are selling at, and people _think_ that the price point should be lower.
The issue is that the lower price point in the case of piracy appears to be free. People still pirate $1 iphone apps.
this is a very key quote - it indeed drops the rate of piracy. But does it increase the profits earned correspondingly? that is, did the anti-piracy measures contribute positively to profit?
I am unsure what the case is in reality, since its so hard to compare. Most pirate's intuition is that anti-piracy measures don't increase the profits (or unit sold, so as not to complicate currency+accounting issues). Companies that use anti-piracy measures seem to think the exact opposite.
I don't know what juicy license terms would be , considering I can stick a flash or HTML5 video on my website without paying adobe or W3C a cent.