It hardly matters if they put the sponsors in or not -- I personally skip the introductions to all the movies I watch, why should anybody not skip the sponsor list?
And I doubt anybody would upload a tv series episode where the commercials hadn't been cut out.
Advertisers and content producers seem to have a problem with people skipping their ads, going so far as to sue DVR makers for including a "skip 30 seconds" button. Clearly they believe there should be some kind of social contract[0], where they expect viewers to view their ads in exchange for watching the associated content. Such a social contract would be far more likely to be upheld if the ads consisted of a simple and informative list. Dedicated fans of TV shows will sacrifice ten seconds in order to support show creators. For that matter, they don't even need to watch the sponsor list for the full 10 seconds, as long as they know it's there, and that buying goods from those sponsors will keep their favorite show running.
[0] Actually it seems they want the force of law behind their business model...
And I doubt anybody would upload a tv series episode where the commercials hadn't been cut out.