Drums can sound inherently boxy. Annoyingly even. And those boxy frequencies reside in the mids, around 400 Hz or so. Maybe a little lower, maybe a little higher. But if you boost the mids, scan the spectrum and cut when the boxiness pops out, you've immediately made your drums sound better. Just by cutting the mids you've subjectively boosted the lows and highs, since the spectrum now looks like it has more lows and highs than it does mids.