Some may not have the money for such expenses.

Some may have ethical issues regarding how the CEO invests his profits into military companies. And Spotify makes less money with ads than with the subscription fee.

Some don't want to pay for ad-free Spotify, since the subscription fee is much higher than what they make with ads. They don't see the price as justified.

Some prefer other ways to listen to music, since they have an issue how a plethora of artists don't really benefit from Spotify and are rather exploited. (Okay, those listeners are probably not meant here anyway as they are not affected.)

Some have a problem with such subscription services, especially if you do not own a copy of the music and there is a risk of the music, they like to listen to, being removed from Spotify's library.

Some especially don't want to pay for Spotify if they removed a feature, miss a feature or moved a feature behind the subscription, if that feature was previously available or should be available, because there are some things which are taken for granted or are usually expected and they protest against a business model of "creating value by taking something away".

Some may be cheap, yes.

But surely not all of them. There can be many reasons and it's usually a good idea not to shove all people of group X into a single drawer and judge them in such an inconsiderate way.