If you're a tiny rights holder, you may have produced a single song and are trying to make sure others pay you for use - but you may not be able to afford or understand what legal review you need.
If you're a major rights holder, you may have so much content to protect that is so wildly popular it is impossible to review manually. But automated review with 100% accuracy is not possible.
DMCA in many cases is not fair, but I don't think we as a global society have much of a shared view of how to handle digital creative content. Ease of digital replication doesn't match how much we generally value creative content.