It's a case by case situation. When I was younger I tried to look for a reason to compress everything but as I got older and understood compressors much better, I only use them for very specific situations.
I use EQ's to tame down certain frequencies that are problematic. Now lets say there's an instrument and every so often a certain frequency range kinda goes up ruining the sound, I would use a multiband compressor to just compress that part ONLY when it goes too high. That way I'm not compressing the entire sound but just this frequency area that comes up once in awhile. Another reason I would do this is if I use an EQ to carve that part out, that frequency area would be lowered the entire time which can take away some color away from the overall sound. I only want it to be reduced when the problem does happen. You really have to see the problem that calls for the compressor. And of course you can use it for a certain effect you want, which is all subjective.