I don't understand why there has to be a separate network address. Aren't the DSN submask and the network broadcast addresses enough to identify a network?
Networks need specific addresses to support routing. Routers are configured to send traffic to different interfaces depending on the network address. They usually do not care about the specific host unless they are a router on the same subnet as that host.
For example, you send traffic from your PC, to your home router, which forwards it to your ISP's next level router. That router is likely not directly connected to the destination of your traffic, so it will be forwarding it to another router that is closer. This is all based on the network part of the address and not the host.
Network addresses are also important in "route summarization" which allows routing tables to be shorter - very important when hundreds or thousands of routes are involved.