Some of you guys are hilariously ill-informed
Sound is like colours: it can be warm, cold, distorted, etc. Saying you don't need an equalizer is just as naive as saying you don't need to calibrate your computer screen and claiming the picture is meant to be displayed that way. Seriously: that's ridiculous and wrong.
Every device you buy, will have deviation of perfection. Some screens will tend to be more blue, some more yellow, some more red. Some speakers will have more bass, will be tinnier, etc. Some mp3 players will exaggerate the lower tones or higher tones, feel colder or warmer.
THAT is why you have calibration. On top of THAT, you got pictures that have distorted colours - the white balance is wrong, the blacks are not pure black but dark grey, etc. With music, this is no different.
So if you claim that AFTER you have a potential distortion on the speakers AND device AND medium, it's not needed to do any alteration, you're living in CUCKOO land! Ideally, every song would need its own equaliser setting depending on the device and speakers/phones used but at the very least, you can compensate for your software/hardware.