After years of reading newspapers, I've never seen a paper that said, "sorry, not much happened yesterday, so today's paper is shorter than usual." In fact, the length of the paper is virtually always driven by the number of ads, not by the amount of news (wars, elections and disasters are the exception). Editors are told how many pages of stories they can run by the publisher, who bases it on ads sold.
The web, of course, doesn't have the problem of paying for paper, so the length of a website isn't driven by ads, it's driven by reader attention and writer fatigue. If you run less material, then readers with attention to spare will just go read more on someone else's site. Hence the temptation to write more and more and more and try to milk pageviews.
The same math works for direct marketers and brochures. Since it's free to keep writing or to make that video ever longer, it's tempting to do so. Might as well keep talking until the reader surrenders and buys something.
Here's the problem with that math: people like to be done.
Sure, there will always be a few who want more, but you're often better off giving the majority a sense of mastery and a platform to take action.
Just because you can write more doesn't mean you should.