Hours are just shorter on YouTube than they are in movies/streaming services.
(It just occurred to me I have effectively watched tons of documentaries.. they just were on YouTube and not called documentaries lmao. Weird how brains think of these so differently, at least for me)
People generally watch YouTube videos more casually, including with more pausing and often while doing something else. It takes less energy to watch a long YouTube video than a movie, whereas with short videos you can't just sit back and relax and let it play, you have to bring up something new almost immediately if you wanna keep watching stuff so your attention has to be more focused.
When binging a series, don't try to stop at the end of episode. It usually has enough cliffhanger to compels us to watch next episode. Just stop on scene changes, like when there's a fade to black and the location changes
This is exactly what I did when I recently watched The Fall of the House of Usher. After the first episode, I knew each ending was going to make me want to keep going. So i would switch it off when it would change scenes and come back to it later. Made me feel less like, "omg, I really need to see what's going to go on next." And made me realize I should do it more often.
Episode pacing is different to movie pacing. More opportunity for story arcs, payoffs, etc than in one 10 hour movie. It's completely logical that someone should be able to more comfortably sit through and digest 10 episodes versus a 10 hour movie.
Also, the commitment for a 3 hours movie feels like a lot when you have to be invested in it the entire time. And it isn't made to have pause breaks, so pausing always feels awkward.
At least you can guarantee a break after an hour with a series.
That was the point of intermissions back in the day. We just need periodic breaks to process what's happening and keep the stream of information in digestible chunks.