I was thinking of using key files for remote SSH access to my server instead of entering the account's password manually at login. On the Internet I found several tutorials on how to do that for Putty, which I am using. All of them recommend to protect the private key file with a passphrase. That makes perfect sense, as I don't want anyone who might gain access to that private key file to access my server without password.
However, then I was asking myself: If I need to enter the key's passphrase every time I use it to connect to my server, why should I bother to use key files then at all? I could simply continue to enter the user's password directly.
Unfortunately I could not find a good answer to this question online.
So I would like to ask you here. What is the reason for using a password protected key file for SSH authentication, instead of simply entering the user's password directly?