Relying on Flash or Silverlight is similar. I use Linux, and Flash is officially unsupported on Linux. Silverlight has never been officially supported on Linux. If these are the options, then I cannot watch the movie out of the box, I have to find a flash installer (I had better hope one's in my package repositories), or I have to install wine and build Silverlight into my browser or some such.
I think it is totally reasonable that you would ask the studios to provide content in a manner that you can actually watch. Let's not even get in to the Blu-Ray encryption snafu and how that affected those of us who use non-commercial operating systems.