(It's funny, I mentioned this to a coworker from the EU and he asked why the intermission wasn't enough for this. I'm still not sure it wasn't part of a joke that I didn't get, but I think at least US movies when shown in theaters around him always have an intermission.)
At home, we can pause for bathroom breaks, snacks, etc. once or twice during a movie without too much interruption but with zero missing of scenes or annoying people as you squeeze back and forth down the rows when you need to get up.
What changed was big home televisions got cheaper, and those of us who value decorum during movies can get it at home, with cheap snacks and the ability to pause the movie.
Similar to the difference between going to a restaurant to eat versus just getting takeout from the same place.
There's only three theaters in town I really enjoy visiting and then only their main auditoriums (~700-900 seats). My favorite has (or at least until recently had) the largest THX certified auditorium[1].
If I can't get the proper big screen then indeed it's better to just watch at home.
That said, it helps that the audience here is for the most part quiet and sitting still.