So now when I want to find videos on a topic, for many of the videos I’ll get a hundred hits for the same video uploaded to each service. But if the one I want was only uploaded to one device, it’ll be buried in a sea of hundreds of duplicates.
If using a search engine is the ordinary method of discovery then there would be no need to upload the same video to multiple services. Meanwhile if people did that anyway, the search engine would want to figure out how to merge the duplicates.