Not to mention people falling asleep means that all ads will play unskipped, regardless of length. That means they have data that non-zero amounts of people are watching the whole of the extremely long skippable ads that get placed (more than once I've seen 90+ minute ads appear).
> people who use youtube as a sleep aid - don't you get woken up by ads?
I pay for Premium for that reason. I don't have any other TV/streaming services, so while I don't especially like giving Google money, I use it enough that the expense is well-justified.