Why does 'apt-get install' suggest packages that I already have?

On Ubuntu Desktop 10.04.1, I have just run apt-get install to install a package. Amongst the list of suggested packages is ssh. I'm confused, because I am sure that I already have ssh installed: # ssh --version usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-e escape_char] [-F configfile] [-i identity_file] [-L [bind_address:]port:host:hostport] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] [-R [bind_address:]port:host:hostport] [-S ctl_path] [-w local_tun[:remote_tun]] [user@]hostname [command] So... When apt-get install suggests packages, does it take my existing set-up into consideration before making the suggestion? If so, why does it suggest something that I already have?