Your reputation within the comunity is important. Just as an example, I joined a PF group to do ravana, notice this person that dont do his job properly or die a bunch of time so I remember their name. Other day I joined a PF and notice the same person so I reconize it and left. Sudently he send an application to join the FC and the leader ask if someone knew him so I see the name and can share my bad experience with him. If that person could name change often I would never notice and would hace to relive the PF waste my time and we would had a bad player in the FC.