There's a difference between sacking a city and razing it to the ground.
In terms of "We, as a nation, does not care for this city at all anymore and will cease any support immediately. Anyone living here will be relocated and/or killed"; No, not really.
That doesn't destroy everything though. Maybe if it's a small city than yes, you could just burn down the huts and other small buildings which would probably be made of wood. But in a large city there would be walls and buildings made of stone, which aren't so easily destroyed.
While entirely true, in the context of what we want to do - remove any and all support from a city and basically take them out of the proverbial equation - "Razing" a city is ridiculously easy. Especially as an seemingly omnipotent despot.