Looking at it from a defense-in-depth perspective, its another layer of protection. Even if you use fail2ban and mandate key-based logins, it answers questions

Looking at it from a defense-in-depth perspective, its another layer of protection. Even if you use fail2ban and mandate key-based logins, it answers questions like "what if there is a 0day for my sshd?" Its not a bad idea, it just happens that careful sshd practices are good enough that more layers are subject to highly diminished returns.