Some of the reason behind is separation of concerns strangely enough. I work from home, we live in a 1 bedroom apartment, and I felt really stressed whenever I would play video game or watch TV while still in the very same space I worked all day. I was basically doing everything in the same 10sqft all day every day. Now, because it's in another room, I feel way more relaxed.
Another plus is now I get the sun up right in front of me from bed every morning and that's just an awesome feeling I didn't get from the bedroom. I believe the bedroom should be oriented south east to get that morning sunshine to wake you up, and we didn't get that before.
I would joke with my parents "why is it called a living room when we can't live in it"
For context, TV at that time meant a handful of channels received over the air, and a "big" screen was 19 inches.
I guess I've kept a similar pattern. My TV is in a little dedicated TV room. I have another wall-mounted TV but it's mostly just a big digital picture frame. [ADDED: I watch TV/movies but I don't really like to mix it in with other activities for the most part.]