Because it's a gigantic time sink for 200-400 DPS. That makes the entire concept of crying over having to do it rather pointless.
PA is just there to give people the feeling of progressing past the point where progression stops. But at the end of the day, your raid won't miss your 200-400 dps.
200-400 x 12 or so pure DPS in your Infernal Dawn raid WILL be missed though. You can't just judge this kind of thing on an individual basis. Also, have the 750 or so extra hp for the entire raid is incredibly valuable. It's almost the same as having a double heroic endurance pot while still running an earth or fire resist pot at the same time. If you think that's trivial then you should probably stick to measuring your epeen on worthless Plutonus parses or something, and leave the real raiders alone.