Players have differing tastes and as such not all content appeals to all players. Those labels are attempts to define content by the groups of players that enjoy them.

For example, a hardcore player might find casual content boring while a casual player might find Hardcore too stressful to be enjoyable. As such a hardcore player will value casual content less and vies versa.

Since devs have a limit to the amount of content they can create, players naturally argue over which type of content the developers should focus on, usually favouring their own preferred type of content.

Humans are hard wired to try and define and organise things they see into systems they can understand. There's a case on a American army base where a pigeon language was used to communicate between varying nationalities where children growing up of the base naturally developed a grammar system for the language subconsciously as they learned it.