Networks are easy. They are by far the easiest way to share data and resources throughout an office or even your house. Networks are easier to use than modems for internet access, and more secure.
Many people feel that they have no need for a network, or that it will take too much time to maintain. However, a properly set up network has minimal points of failure, and faults are easy to diagnose over the phone.
More and more network devices are configured and managed via web interfaces, so you can tell if the downstairs printer is out of paper before you walk down there to collect your document. Home networks can be configured for music streaming technology, which allows you to save all your music and video collection onto one machine, and watch it over the network on any or all the computers on the network.
Networks are safer than dial up connections, especially with ADSL, because the device making the connection to the outside world is harder to compromise that a PC running all sorts of programs.