That seems an overstatement. I now have one in my entire house (don't have kids).
There's a fairly large TV panel on one wall in basically a sitting room. Otherwise I just use a computer. A relative basically has TVs in every room. I guess it maybe made sense when he was rebuilding anyway but it still seems excessive to me who might sit down to watch a movie or show but doesn't have live TV.
But, then, I don't have AC either in Massachusetts.
Ambient light is dealt with having nice thick blackout drapes.
This is not some rocket science, it was done for like a hundred years.
edit: actually in my former apartment I just bought a roll-down projector screen that completely covered the window. pull down - zero ambient light even in full sunshine.
Take a look at this house:
https://www.zillow.com/homedetails/5619-Walnut-Hill-Ln-Dalla...?
Sure, it has a theater room with probably an incredible projector I'd imagine. It also has a bar with a big TV behind it. It also has a game room with several TVs mounted on the walls. In both of those situations, you wouldn't really want a projection setup. A brighter TV wins out in the end.
I've seen lots of TVs mounted in outdoor living room/kitchen arrangements. They're common to find in living rooms even for people who have separate theater rooms. I've seen them mounted in garages. TVs have uses other than just pure cinematic experiences. And I say that as someone who has personally pushed TV watching to an exclusive space in my home and made a point to not have TVs everywhere. Other people like different things.