I know that a lot of people like to listen to music while they work, but I am not one of them. Often it is in the form of a random news channel on the TV, or (unfortunately not during the COVID-19 shutdown) a Cubs game lilting just within earshot. When I work from home (WFH), I like a little background noise. But what if you listen to Spotify on your Mac? What about YouTube or streaming music in a web browser? Unfortunately, there is no built-in EQ for Safari, nor is there a way to control the EQ on a system-wide basis. It can help compensate for the small speakers on your MacBook Air or MacBook Pro or fine-tune the bass and treble in your headphones to your personal tastes.
The Apple Music App has an okay (i.e., usable) equalizer with plenty of presets for the average user.