Here's another reason...
I was just messing with some Merged profiles, when I setup the Merged profiles I used my CLR FRFR monitor and added a highpass/lowpass filter in the X slot to dial it in because ultimately the most important sound is what comes out of the mains. But when I disabled the cab in the monitor output to feed my 112 guitar cab on stage the highpass/lowpass filter was still affecting the signal going to my guitar cab which kind of messed things up. If we had a highpass/lowpass filter built into the cab slot it would work perfectly in this case because it wouldn't affect the signal going to the guitar cab if the cab is disabled in the monitor output.
Here's hoping the Kemper team hears our request for this feature