It's like pizza, ya don't eat an entire pie, you eat the slices cause it's easier to manage.
And then you realize an hour later that you went through 3 pies slice by slice.

I think one thing that ought to be considered is the structure of most online videos; a ten-minute video is often put together in a much more manageable format than an hour-long video, and as a result it's easy to go through several ten-minute videos without issue compared to one video long enough to count as a movie. Additionally, most hour-long videos aren't actually built like traditional movies or documentaries, but are rather lengthy video essays, and as such the attention required for them is difficult to muster compared to the attention required for your average mainstream film. I can sit down and watch 2001: A Space Odyssey in one sitting without a problem, but for something like YMS's "Disney copied Kimba" debunking, a video with a similar runtime to 2001, I prefer to watch it in segments, simply because of those fundamental structural differences.