Well, I'm guessing it's because YouTube has cracked down on what it will allow to be posted ... on some of my videos, it's just those videos and nothing else. On others, where YouTube (I guess) can detect copyrighted material, there will be ads, and links to Amazon to purchase the song being used, etc.
Facebook doesn't quite seem to have that issue. Then again, I uploaded it to Facebook and set the privacy to extremely narrow parameters; only about ten or so people can see it and they're all people I know from the BBS. But, it's high quality and does not have the same blocking issues YouTube apparently does.