YouTube offers millions of dollars in free advertising to content creators along with tens of dollars in free hosting.
It really doesn't. To understand why, you have only to comprehend the following: Whether someone is searching under a particular keyword, or just browsing whatever pops up on the home page, the average browser has a finite amount they're willing to scroll before abandoning their search... and chances are your video is NOT going to be placed highly in those results unless you're directing a firehose at it from offsite via Twitter, forum posts, news aggregators, or paying Youtube to promote your video flat out (which is such an obvious moneygrab on their part its disgusting). In other words: If you rely on their algorithm to promote your work you're literally playing the lottery and, much like the lottery, statistically you're going to lose. It makes far more sense to find bandwidth and hosting, negotiate with an ad network, and direct a firehose at the resulting site... but that's more work than some are willing to do. shrug Oh well.
Indeed, I was just trying to point out some decentralized alternatives.