Maybe only if you want to store the key on a separate physical device, and it only supports RSA?
Those are needed for example to push code to their managed git (CodeCommit) and if you want a key added when you launch an EC2 machine and to fetch the Windows password.
Edit: Another reason one might still use RSA keys: ed25519 isn't a FIPS-140 approved algorithm (yet).
My almost 10yo yubi still works just fine.
But beside the point as we are talking about RSA 2048 here which is in fact "perfectly secure" and the public key is not the part subject to downgrade attacks.
The benefit if you do this is now you can impersonate the key's owner for new connections. So if it's a host key you can pretend to be that host if you're able to get on path between a victim and the real host, if it's a user key you can log in as that user with public key authentication.
But that's an active attack and an expensive key break.
Breaking 1024-bit RSA for HTTPS servers was a much juicier target because you can passively snoop RSA kex in TLS 1.2 and older. But that's not a thing in SSH, it's active attacks only.