Ever hear of certain speakers being better, or worse for different kinds of music? That's what I use the EQ for. Also for what I know certain bands were known for. Take Van Halen, for instance. Eddie Van Halen was known for developing, or emphasizing that "brown sound." I know that sound for adding a distinct quality to their overall presence. Others have that sound as well and other variations of intentional types of distortion. Randy Rhodes from Ozzy was another with a trademark tone. That's also what I use the EQ for.
Roy Buchanan, yet another. Stevie Ray Vaughn's Strat, with the jumbo bass frets and the heavy strings, right down to the weight of all the rings he wore on his fingers that affected his tone somewhat later on. Billy Gibbons, in spite of having a heavy sound, actually used light gauge strings.
All these things I learned from seeing live performances, I would miss if I could not help it with the EQ. Some systems correct these nuances out of the music because to them, it registers just as distortion. Distortion is bad, unless it is intentional, and then it can be good, at least with electric music.