The answer is pretty simple. They're trying to force an internet model onto a television service.
Internet advertising is predicated by the need to get users to click as often as possible. Every page of a commercial website will have two or three ads and they will be paid either per impression (CPI) or per click (CPC) in either case, the onus is on getting the user to move from page to page as rapidly as possible - hence the pagination you find on websites where even the shortest article is spread over three pages.
Television advertising operates on totally the opposite principle - that the viewer does nothing except sit back and watch - the longer they do nothing the better the revenue as they lap up commercial after commercial.
So, YouTube's woes stem from trying to combine the above. There is an easy solution, but I'm damned if I'm going to give it away for nothing!