Why, precisely, do you think you can't play the video file in a player of your choice? That is literally what DRM is - technical restrictions against using content you have purchased in a manner you desire. They provide the file in an encrypted format that only their own player can decrypt.

When iTunes used DRM for music, only Apple's devices could play music you bought from iTunes, too.

However you're right - the iTunes purchasing example shouldn't have been part of my previous response. On the other hand I think DRM is fine, if not a necessity, for a subscription service like Netflix. It is basically renting content and my expectations towards these services are very different from a store that offers purchasing, which should absolutely be a DRM-free experience. The fact that it's not is exactly the reason why I don't buy films on those platforms, unlike music, which is available countless large and niche stores.