Clearly OP you don’t understand the purpose of the luck benefits of being PVP flagged.
The players who are flagged PVP need pvp gear and that means likely not having gathering luck on it. So the benefits of the buff replace their baseline gear. As a PVE player you can get the same luck by just wearing your gear and not flagging. Having both doesn’t provide any huge noticeable difference.
Players that PVP need resources to craft too. Fighting over those while flagged makes a lot of sense and is an avenue of game play.