Because you all hit us with so many Abuse Reports so fast we have to ZOT them to get back to the real work :-}
I suppose the problem is that there are so many trolls and disrupters flooding into the forum that it would be a practical impossibility for the mods to make a mental (or even physical) note to go back later and delete an account after Zot thread number 769 had run it's course. IOW, and figuratively speaking, the moderators have to pick up the trash and toss it when they first walk by. With their workload they can't be expected to say to themselves, "I'll come back later to dispose of that empty beer can or that used condom."
Nevertheless I agree with you. The Mods are spoiling our fun. I wonder if it would be worthwhile to build a "delayed ZOT" feature into the forum software, so that a mod can press the button on a troll but have the deletion of his account delayed by a certain amount of time? Alternatively, or in addition, the troll could be prevented from posting new threads, or even restricted to replying in a specific thread.