Comps are usually pretty subtle effects; you want to play-around with them a bit and develop a 'touch' for using them. If you're primarily a rock player (like me) with a heavy touch/strum (like me lol), then the compression effect quickly gets lost. They're subtle effects, usually; and work best with a subtle touch (usually, IME).
I'd say if you're doing a lot of lead playing, single-note lines, etc. then a comp could be a useful tool for you. Among a small pedalboard of 'standard' effect boxes, I often pass on mine. I often find a boost pedal works just as well. IME, YYMV and all like that.
Need is subjective...and the usefuleness of compressors are very rig/gig dependent...but I'll say, once I got one and understood how to use it, it became a pretty important part of my sound, esp in a live context.
If you are a Les Paul through a Marshall guy playing hard rock or punk...probably not.
If you are more a Strat/Tele through a Fender playing poppier stuff...probably most definitely.
i went back and forth on using my MIJ Boss CS-3, but recently I've fallen back in love with it. use it on all my finger picked stuff, really helpful for boosting volume without adding too much gain while maintaining clarity in a band setting.