Several reasons:
Consumers don't usually like a copy, they think of it as a knock off, even if it is better.
Sony is already "all in" on a tech platform, they should focus on making appealing content and marketing the existing platform.
Sony's strength is the Playstation Brand (yes, not as much as it was, but still good) and the image as the high tech, feature rich platform. They can still push the PS3 as a set top box, internet-entertainment device.
Personally, I think Sony should do some marketing with some internet companies to show the benefits of the PS3.
I pretty much hated my PS3 until I found out I could watch Hulu.com on it. They should cross market with them and maybe some of the music services, rss feeds, etc.
I would cite regulation, but I know you will simply ignore it.
