1A has a higher % of HO seats than other classes, which are obviously unutilized, which in turn are offered to current reservation..
Regarding train running full, obviously, even mid-week, 2A,3A and SL show No availability at all, even after charting.. shows the popularity of the train..Due to which I guess, railways by keeping KK RSA are losing money (If KK-Mail RSA is broken, Railways could've replaced PC with maybe B4, which in turn can fetch revenue for IR)