There is no conceivable way random consumers can identify whether a random video violates someone else's copyright. Every consumer would somehow have to be familiar with every video in existence, and who owns it, who they've licensed it to, and all those people's identities on every platform.
Imagine if making your comment here required you to investigate the originality of several other comments and whether the posters may have posted similar things elsewhere under other names, or licensed someone else's content, or violated someone else's copyright. Would you still bother posting?
If you can't trust a user to identify copyright violations in someone else's work then you probably should blindly host content created by that user either. I think people would learn how copyright works so that they can prove it and earn the right to post on a platform with massive distribution.
Imagine if making your comment here required you to investigate the originality of several other comments and whether the posters may have posted similar things elsewhere under other names, or licensed someone else's content, or violated someone else's copyright. Would you still bother posting?