I've found that there are 4 main categories of gameplay in DayZ:
Those who play in a group, and are bandits
Those who play in a group, and aren't bandits
Those who play solo, and are bandits
Those who play solo, and aren't bandits

As someone who plays the last category, if find that I have nothing to gain from continuing to play once fully geared. I can try to be a hero and help other players, but more often than not I just end up dead and losing my items. I myself am not a fan of losing hours of gameplay spent traveling and gathering equipment, so I don't take pleasure in killing other players. Since I have nothing left to do after becoming fully geared other than die, I find myself disinclined to play.

I wish I had a constructive suggestion of how to fix this, but I hope that you guys, the devs, can keep this category of player in mind during future development =)