From what I understood, it was to allow cross compatibility with SteanID and its Epic Games Store equivalent. Up until FLS was put in, all players were identified by their SteamID. EGS players would not have SteamIDs, so they wanted one system that both tapped into so that players could be identified for both servers and mods that utilize such.
EGS never happened. So we have a system that isn’t needed. But taking it out would case a bit of a headache for both Funcom and private server owners, as well as mod authors.
As for my opinion, if EGS isn’t going to happen, then we should FLS removed at some point.