There are a finite number of known movies. There are an infinite number of "bad" videos that could be created. It's easy to come up with an automated system to

There are a finite number of known movies. There are an infinite number of "bad" videos that could be created. It's easy to come up with an automated system to identify the former, orders of magnitude harder to create one to identify the latter. Not to mention there's also an infinite number of benign videos that could be created, and you need the automated system to correctly identify between all three for most of the time, otherwise one group or another is going to get mad at you.