Almost every game has various leaderboards just for fun. It doesn’t have to involve additional rewards that changes the gameplay.
I.e leaderboards for xp (even if there’s a cap on level there’s no cap on xp), highest stat, such as luck perk, SP, even unit perks.
To not disrupt the balance of the game, cosmetic rewards can be given. Such as, if a person has the highest perk recorded for pyromancer, his pyromancer can have a new skin colour, one that glows or something. Another example would be the hero with the highest luck perk can have a rabbit face instead of a human one, etc etc.
It’s just for fun and for bragging rights.