Let me rephrase. It makes perfect sense that iCloud Photos works EXACTLY the same way as iCloud Contacts, iCloud Calendar, iCloud Notes, iCloud Reminders, iCloud Keychain, iCloud News, iCloud Safari. It would NOT make sense if iCloud Photos worked differently from every other iCloud service. None of these are archiving services. There is no reason that iCloud photos should be different from every other iCloud service.
You CAN move videos and photos to iCloud. If you do they will be replicated on every other device that is logged in to the same iCloud ID, as well as to https://icloud.com. EXACTLY the same way as moving a contact to iCloud; It will be replicated on every other device logged in to the same iCloud ID as well as to https://icloud.com.
Whether it makes sense to you or not doesn't matter; that is the way it works, and the way Apple intended it to work. There are dozens of archiving services on the Internet; iCloud is not one of them.