Simple.

Endgame Raiding involves working with multiple people to clear usually well designed, engaging, challenging content, which provides gear that is useful for the subsequent more challenging content.

Endgame Crafting/Gathering in involves working with yourself (and your mouse, and your free hand if you're bored), to perform mindlessly simple repetitive content which is often time gated on an hourly and weekly scale, which provides the "opportunity" to have a chance to obtain gear which is useful for... nothing... because the mindless repetitive grinding and 5 minutes of crafting you did to obtain this gear is already the very pinnacle of your available content.