The main reason for me is that there is not much of a reason to PvP in terms of lore and story. Every time I have been attacked by another player (except for a couple of arranged RP PvP meetings - more about that below) it was somebody shooting at me without saying anything, without making demands, without me being wanted or having a bounty on my head or carrying precious cargo. So, I had no clue on WHY this commander was shooting, except that he probably got some thrill from the fight in its own right.
The game does not promote meaningful PvP: piracy hardly works, players are in both the Federal and Imperial army at the same time, the only thing which somehow makes players chose a side is PowerPlay which is problematic in its own right. Also, due to Peer2Peer networking and the way instancing works makes it very random with who one turns up in the same instance, which again makes PvP rather void of meaning. There simply is nothing to fight for.
I did try to go against the meaningless PvP: in the beginning of the game, Beta and Gamma times and just after the launch, we tried to organize Role Playing PvP events among several player groups. Problem was that we got no traction, we remained a small group, and of those I am now the only one who still plays the game. Forum policies also did not help, since our announcements were hidden in subforums where hardly anybody was looking. I tried to set up an umbrella organization to bring groups together where players just attacked other players in case the other player would be wanter/have a bounty, or if the players belonged to factions which had some war or feud between them going on, in stead of just "for the lulz", but I failed.
Later on, the Engineers introduced a schism among the players who do go through the grind to get their weapons and ships upgraded, and the others who have no fighting chance against the first group. So, when I returned to the bubble after a long exploration tour, the only option was to join Mobius or play Solo, since in Open I would not stand a chance until I go through the Engineers. I have no problem being killed by a player with superior skill, never combat logged when fighting in Open, but now I do not see the point of risking to get in a fight against over-tuned bazookas with my knife. I might return to Open if Beyond somewhat levels the playing field again.