Lets say that you have all of the latest and greatest electronics in your house. The down side is that It doesn't matter how awesome or fast those electronics are designed to be, because their network reliability and control speeds are going to be completely dependent on your Local Area Network (LAN). The Wide Area Network (WAN) is what's in charge of your download and upload speeds. Your (WAN) speeds are dependent on your Internet Service Provider (ISP). There is no need to pay top dollar for 70MB download speed for watching movies and streaming music if your running all of devices through a slow outdated router or network switch.
You simply can't have a conversation about designing a Smart Home without assuring that you have a rock solid Local Area Network (LAN).
Music Streaming, Airplay, IP Cameras, Remote Access, IP Control, File Sharing, and MORE are all reliant on your home or business network.