The title is a bit misleading but here it goes. I'm sure everyone have seen enemy realms, allies and sometimes your own realm begin a TO not for the sake of completion but other purposes. Like denying the enemy fortifications, taking the advantage of being the defenders and able to dig in, denying the enemy any tax income, closing down important buildings, etc. In most of the cases the TO is abandoned soon.
My question is whether this behaviour is okay or not. Is this a strategic use of TO mechanics or just another abuse?