Microsoft’s issue with Silverlight is a regulatory issue– it has the means to distribute Silverlight to every Windows box connected to the internet but it can’t because regulators have a watchful eye on everything that the software behemoth is doing these days.  It’s hard to find a more frustrating situation than that.  So the company has no cost advantages in user acquisition vis-a-vis other desktop software apps.  Link. 

Microsoft is taking several approaches to trying to boost Silverlight’s
distribution, ranging from striking third-party deals like its pact to power the NBC Olympics Web site to bundling Silverlight into other Microsoft products.

Although Goldfarb didn’t use the word "bundling," he did say Microsoft
is actively trying to get other product groups within the company to
adopt Silverlight in some way and then distribute it as part of their
product.