It's not that, it's that you have to have your router in control of not only your LAN but your internet connection as well.
There is (was) no other option. I use a router, but just as a pass-through device connecting my wired and wireless LAN devices. My Linux box actually controls the LAN and is the internet gateway for the network. If all you have is DHCP then the device will connect to the router and assume it is also the gateway. Far, far too simple for advanced users.