Oversimplification.
This one is justified visually, by the signage in big record shops, as a purported improvement over listening with your ears. This is the one that says listen with your beliefs. And, this is a form of compartmentalizing personal experience.
Of course, most artists reject categorisation of their work. It's insulting. It demeans and diminishes what the individual is capable of.
Some artists will create a successful brand for themselves, support that primary goal with enough consistent work to begin to develop an artistic thesis – but then find that after a few years, shifting and evolution is something that typecasting resists.
And naturally, without categories, so many people argue they couldn't discuss music otherwise, like it needs to be converted into a verbal abstraction, or architecture for the masses.