If I wanted to use one mix to send to the subwoofer amp, and another mix to go to the mid/high amp, it would be nice to put a steep-slope low pass filter on the former, and a steep slope high pass on the latter.
This is possible on at least one competitive unit, and it actually works pretty well.
…and I’m sure A&H would do a better job of implementing the Butterworth and L/R filters anyway!