Ask yourself this and you will answer your own question : Why do you play in mobius PG instead of Open mode ruled by Fdev ? Like you said, it's not because you can that you should.
I have an interest in this question, so I'll offer an answer.
I play in a PG, and specifically Mobius PvE, because that environment fits my view of how the E|D Galaxy would really be like. I just don't believe the Pilots Federation would tolerate members attacking and destroying other members. This, coupled with the idea that I don't need to prove a thing to anyone, and I am happy to concede PvP victory to those who desire it.
I can, happily, accept the notion that other people play the game for other reasons other than myself, and be content knowing that FD have accommodated those differences with it's design of the Mode System. In short: I can play E|D without expecting everyone else to see the game as I do.