Many devices ship by default with their Network Standby feature turned off. As a power saving measure, the network interface of the device is shut down when the device is turned off.
This feature can often be turned on in the setup menus of the device, and is necessary to operate devices entirely via IP.
A very small number of low-end devices do not have a Network Standby feature and thus cannot be turned on via IP even though they can be otherwise controlled via IP. The IP compatibility list denotes such models when we become aware of them.