In-Game Parser.

[Taika]

Nothing, I don't need programs to make myself better or my team in order to win a fight.

I just don't understand what you need parser for other than attacking others because they slow you down.

You do not now how good you're doing without a parser, DPS wise. Mechanically, you do know, because you know how you move and if you're evading stuff or not. DPS wise, all you know is if you seem to be following the optimal rotation (based on what someone else has parsed) and that things are or aren't dying fast enough with your group. But you can't know if you're doing good damage for your item level. And if your group fails to pass DPS check, you don't know if it's you who has to do better or someone else.