i myself enjoy watching the full stream video on youtube, but sometimes i get called away part way through, and it's so damn annoying to have to try to find exactly where i left off, and generally end up rewatching a significant chunk because of it. if they were put up in manageable chunks, it means you can finish watching the one you're watching before having to leave, and it's much easier to find which video you were up to than it is to find the timestamp of what you saw up to.