As other's have pointed out, they are contractually required to use DRM by the content providers and it's not really effective anyway.

But what really annoys me is: I want to watch netflix on my TV, it's a little too far from my Computer so I have a Raspberry Pi hooked up to it. The Pi is fully capable of running netflix, it can run a webbroswer with html video support and decode 1080p mp4s. But because the raspberry pi foundation refuse to lock down the firmware and provide a safe area for the Widefire DRM plugin to run, netflix refuses to run.

I pay for netflix. Why should I have to buy a locked down device like the Chromecast to use it?