I don't think there's any harm, but it's so annoying for us mums to have to go round the house switching them off after all the other lazyiters have managed to switch them on to charge their batteries, etc, and they can manage to pull their plug out but not flip the switch to off!!!!!!!!!!!!
Not all plugs have a switch on them. On those four-gang extension socket things, they don�t have switches on them. For many people it seems that unplugging something electrical from a wall socket doesn�t necessary oblige them to switch them off.
Sometimes it seems unnecessary when one immediately unplugs something and then seconds later plugs something else in the same socket. It�s a little bit like changing a light bulb when the switch is still on. Obviously no one does this, but you do need to see what you are doing if the light bulb goes in the middle of the night�