In the good old days, most network daemons were just spawned by inetd (plus tcpwrappers). This model took a lot of omplexity away from implementing a network daemon and also meant that there was a central point for configuring the network side for these daemons (like access control).
Unfortunately, the main problem with this approach is that it only supports a strictly one process per connection model and therefore doesn't scale well, so most projects have decided to do their own connection handling now.
The Next-generation Internet Daemon project tries to address these shortcomings by using novel techniques to provide a high-performance, but still centralised connection management service to network daemons.