idk it’s only been in the past few years that member-specific fans have become common enough for it to be noticeable; it’s toxic for the fandom. A lot of them believe that certain members outcast other members, or push SM to give them more privileges than other members, use backstage politics or whatever… and this all leads to their own bias getting a bad deal at the end of the day.
You can see inevitably that member that appear to have more popularity, more work or more exciting and varied work are the ones most vulnerable to those allegations, almost by default.