Why do non-caster DPS do this...?

[MOZZYSTAR]

I am not wasting my Midare Setsugekka, my Tsubame, or my 3 meditation stack Shoha on an add with less than 10% health left.

Same, more or less xD And then once I use up my stronger procs on a higher HP enemy, I go back to the lower hp enemy and take it down with a couple of normal shots.