Turning on electric devices by plugging them in rather than pressing their on/off button
It doesn't matter from an electronics perspective, assuming you're talking about switches that directly switch the main voltage. For other switches, like the power button of your computer, you have to plug the device in first, and then turn it on.

You can see this as an AND. In order for the device to work, both requirements must be met: the device has to be plugged in and switched on. When either of the two isn't met, the device doesn't do anything. The two situations of one met requirement aren't distinguishable for the device.

There might be mechanical issues, as PeterJ and Michael Karas point out in the comments.