I wondered about it myself but I think there's reason for that. DMCA safe-harbor and takedown process only apply to copyright infringement. However DMCA 1201 restricts "manufacture, import, offer to the public, provide, or otherwise traffic in any technology, product, service, device, component, or part thereof [...]". You might want to process circumvention notices not because they are real DMCA notices, but because you are potentially trafficking anti-circumvention tools, you have no safe harbor for that, and you probably want to take it down ASAP to limit your liability.
