I think in a lot of cases (not necessarily anyone responding here!) people simply don't understand what compressors achieve, or try to use them as an occasional effects pedal in a heavy noticeable setting (tone wise) and not understand why else they would really use one, and get defensive when use is challenged. I've seen bassists show them off as an effects pedal, when really the only difference they are hearing that would justify occasional use is a volume boost, because they didn't set it to unity gain.
For me, always on of course, slowest attack and fastest release settings, makes notes just hit harder. Ideal as a finger style player in metal.