You know, most computers and many portable devices allow you to set up a software-based equalizer and tweak the sound output in one way or another. There are also options for improving audio output on deficient hardware, as with a lot of Windows laptops and Dolby/other tech used to male the laptop speakers not sound tinny.

I don't use them, to be honest. I prefer my audio unaltered. Sometimes the "improved" audio sounds wrong.

I usually leave them off unless attached to a cheap speaker system. A common issue with cheap speakers is very poor bass reproduction, and sometimes that bass is heavily distorted.

I did once have a set of speakers that made everything sound like FM radio due to strange waveform compression, similar to automatic volume leveling, except it went just a little too far and clipped.