Well, the obvious one is that it allows you to secure your cold-stored funds securely offline with a metal seed backup and have a separate hot-wallet for spending funds that is also secured by that same metal seed backup without having to compromise the security of your cold-storage.

Another benefit is that I can store some funds for a relative using the security of my cold-storage. You can teach them all about how to manage their own [derivative] seed and how to properly secure and store their seed online or offline, without compromising your own security or setup. That way if they ever screw up, you still can regenerate a copy of their seed and help them recover. It is a great way to gently onboard relatives or people that you have two-way trust with.