Youtube is part of a larger company that makes money in various ways and does profit a lot despite the high costs of youtube. Its existence serves a purpose to google, otherwise they would have already extinguished it or changed the way it operates. To see if its sustainable or not you need to look broadly into the system in which youtube is inserted.

I had a feeling my comment had a noble purpose :)

Considering that drinking coffee is my prefered kind of laxative, i would argue theres actually no distinction between coffee and shit.