In what way? This was true when YouTube first launched (I've heard stories that the founders uploaded copyrighted movies and tv shows themselves) but YouTube has a system in place now that removes copyrighted content automatically and it works pretty well (some say too well).
copyrighted means that the owner of the copyright is the only one with the right to decide when/where/how it gets shown. But if that owner is cool with it being on Youtube, there's no reason for it to be taken down.
You're not wrong, but it's only because that content hasn't been entered into their system or because the copyright holder isn't actively requesting content be removed.
