Lets face it: an integral part of listening to music is adjusting the equalizer. The mobile app has an equalizer, and it is about time the desktop version has an equalizer too. Even if it doesn't come with presets, it should be customize-able for the consumers/listeners.
Just like on mobile, the equalizer should default as a flat line, waiting ready for listeners to change to their liking. In the music industry, one size does not fit all. Sound engineers spend hours and even weeks getting the EQ alone right for songs, because there is no perfect EQ across all genres.
As such, the customer should have every right to modify the EQ to the right settings for their preferred genre. Part of the beauty of Spotify is the wide diversity of music it offers for listeners. It only makes sense for such a business to offer up the EQ feature to compliment this diversity.
Even if Spotify does not want to dedicate the efforts to make this happen, there are plenty of people that would gladly put in the effort for them. I would happily design the feature for Spotify as volunteer work. This feature would be 100% worth it.