What's your use case for it? To have a single seed that secures a master key and then create lots of different accounts that you'd use side-by-side?
Discussion
Actually I'd like to have different accounts for different things. Some things are one time things. But if course it's already possible to have throwaway accounts.
Others are more constant and it would be ok to be tied to an IRL id. For exsmple project or company accounts. Again this could all be seoerate npubs. For other things I want an anonymous account with some reputation.
So maybe it's ease of nsec management and recoverability.