Network logins work a little differently than normal logins. There is a separate physical serial line for each terminal via which it is possible to log in. For each person logging in via the network, there is a separate virtual network connection, and there can be any number of these. It is therefore not possible to run a separate getty for each possible virtual connection. There are also several different ways to log in via network, telnet and rlogin being the major ones in TCP/IP networks.
Network logins have, instead of a herd of gettys, a single daemon (per way of logging in; telnet and rlogin have separate daemons) that listens for all incoming login attempts. When it notices one, it starts a new instance of itself to handle that single attempt; the original instance continues to listen for other attempts. The new instance works similarly to getty.