The use of ALC is not strictly necessary. But... too many folks just don't understand how to drive (or drive limit as the case may be) an amplifier. Worse yet, most overdrive them regardless of any indicator, meter, led, or otherwise. In these cases, ALC helps the rest of us put up with their misguided intentions.
In any case, what you're doing is enough indication to keep IMD and splatter in line. Don't you wish EVERYBODY did?