That's not entirely the case - the application has to run in the environment, and for legacy apps (which most application virtualization is targeted at) Windows is a pretty decent bet.

On top of that the App-V/XenApp packaging suite are top notch and provide avenues for enterprise integrations. (I'm making a big leap assuming it's built on one of them, but it doesn't really make sense to build from scratch, as interoperability/portability would be a hassle)

They seem to be targeting games, so I bet DirectX support is one big reason for using Windows.

Came here to post exactly this.

I was initially excited, wondering how we could leverage this, but now I'm perplexed by: "currently supports streaming applications from Microsoft Windows Server 2008 R2."

I would have thought Linux would have been the optimal server environment too.

If you are at re:Invent, go to the AWS Booth and talk to the team. They might share details on what else is going to come in the next few months.

What mass market application uses real-time, high computation computing? Video games.

And windows still owns the PC gaming industry, though that it changing

Sounds like what AppStream is going for is Windows applications hosting, with the user I/O being shuttled to a non-Windows device. In that case, Windows Server is the only logical choice.