The entire episode is about the flow of information and resources. Just as the Train’s engineers restrict the water pressure to the Tail, your internet connection (or hard drive space) restricts the resolution. Watching in 720p feels thematically correct—you are getting enough to survive, but not enough to truly live in luxury.
The episode highlights that the train is a "tiny world" where every resource, from medicine to information, is a weapon. snowpiercer s01e03 720p