It's real fucking simple, proper fans want to live the hogwarts experience, they want to attend classes with their friends, run missions, compete for house points etc, share the experience with others, for me it's like early World of Warcraft where everyone is running around doing their thing, often times helping out others and completing quests within an incredibly immersive world and leveling up.
For Hogwarts Legacy 2, you make it so all the students you see are other players running between classes to level up their spells whilst engaging in quests etc