It destroys a lot of subtlety and sonic detail in the original, but in exchange you get an overall louder, more in-your-face sound, with highs that come through even on bad audio systems. On car stereos, where you have a lot of low-frequency rumbling sounds, this especially makes a difference. And if you ask a random person to give a subjective quality assessment of original vs that processed audio, they'll almost always feel as if the latter is of higher quality.
For more info see e.g. .
: https://www.soundonsound.com/techniques/multi-band-compressi..., section "Broadcast Applications for Multi-Band Compression."