Because you might like them:
I got to know long-time personal piñatas and found that they were — can you believe it? — human beings, often perfectly nice human beings with perfectly nice families. Even worse, the first words out of their mouths were sometimes, “I admire your work” — and once an author hears that, his estimation of the person voicing this pleasing judgment immediately rises. (She thinks I’m good, therefore she must be good.) At that moment your inventory of ready-made-always-available-in-a-pinch targets would be diminished by one, and since the list is never really that long, the loss of one would be serious. Of course, it might be the case that the person you have learned to dislike in print is even more dislikable in the flesh (oh happy day!), but you can’t count on that and so it is better, all things considered, not to take any chances.
The Dish 