I think this represents our fundamental difference in regards to Open Only. The "non-zero" chance of encountering someone.
Having played online games since 1991,
most of them with environments where "spontaneous PvP" is permitted, I would
much rather have a zero chance of encountering a player who has
no interest in PvP than the alternative. From my experience, the presense of that kind of player does not make for an
enjoyable environment for PvP. In fact, the side effects of forcing PvP upon players who don't want it almost inevitably either completely destroys a game's player base, or reduces it to such a degree that the game's dev team decides adds a hard PvP switch in the hopes of bringing some of its players back.
Despite Elite: Dangerous not having
any of the features that I attribute to making PvP fun, I am actually having
fun with PvP in this game. While
positive "spontaneous PvP" encounters are rare, they are
much more common than other games I've played... which isn't saying much.

Heck, Powerplay related PvP has
entirely positive to date. Granted, it's a sample size of
two, but it still has been entirely positive.
As for
negative "spontaneous PvP," they range from at worst being an irritating interruption, to being something I can actually have
fun with, or even
look forward to, depending from how frequent they are. In games I've played in the past, they're either at best something to be endured for access to the gameplay I actually
enjoy, or at worst something I've quit over, because they make it almost impossible to access the gameplay I enjoy.
I attribute this to the fact that despite Frontier having
no experience with online games in general and PvP in particular, they got the
most important thing right: games are a
social experience, and we should be able to
choose who we play with. Online games have been around for about forty years. It's about time game developers start learning from the
many mistakes of the past.