Posting the video directly still give hits to the video creator each time someone clicks the link to view it.
Web crawlers still find the link on FR and it gains from this busy site as well.
There is no reason to add a middle site running adware except to the gain of a third party, often not the content creator.
Ahhh yeah there is a BIG reason... Youtube gives rankings on the basis of links AND Embeds. in fact it is rumored the embeds count higher than links! Further IF the content Creator wishes He can disable the embedding script for each video he uploads.