Because the only thing that differentiates Open Mode form large private PvE groups is PvP. Open Mode is about PvP and only about PvP, about pure and simple PvP.
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As I wrote, everything other than PvP can be done in a private PvE group or in solo.…
No, you said Open is for PvP only and only PvP. I can quote you again if you need?
I wrote that everything that can be done in Open mode beside PvP can be done in a private PvE group. That's an important part of what I wrote. Remove PvP from Open mode and the result is a very large PvE "private" group. Add PvP to a private Group and you get a mini "open" mode. PvP is the difference between Open mode and a very large private PvE group. If a player doesn't want PvP, but wants to interact with other players in a non hostile way that player can join a private PvE group. If a player joins Open Mode he (probably) gets more players to interact with, but at the same time he's always a part of PvP (he can get attacked, he has to avoid getting attacked).
Since players can't opt out of PvP in Open mode, the main aspect of Open mode is PvP. Every other game mode has the option to be completely without PvP. That can be direct PvP by shooting each other or indirect PvP by trying to avoid getting attacked.
That leads me to my "Open mode is about PvP and only PvP" part: Open mode is a open world PvP mode. Players in Open mode can always* get attacked by other players. There is no way to avoid the possibility of getting attacked*.
The result is, that every aspect of Open mode is influenced by PvP. Every player interaction is influenced by PvP, therefore Open mode is about PvP. Since everything else can be done in other modes Open mode is about PvP. Not being able to avoid PvP is the only thing that differentiates Open Mode from the other modes.
Sure, players can do a lot of different things beside shooting each other and most player do other things most of the time, but that doesn't change the fact that PvP is always a possibility and that (most) players in open act accordingly. IF they don't want PvP, then they can join a private PvE group. Why would somebody play in Open mode if he doesn't want PvP to affect his game play (by fighting other CMDRs or by avoiding getting attacked by others).
In a shorter way: If somebody doesn't want PvP, then Open mode isn't the best choice as there are large PvE only groups where the player can do everything that can be done in Open mode without having to think about PvP.
That's why I wrote that Open mode is about PvP and only PvP. Everything other than PvP can be found in large private PvE groups. Guess I should have written it differently.
…, rather then just saying hi or ignoring, though granted if your experience is that all people do is just say hi, or ignore, I can't fault that a lot do.
Think of saying "Hi" as the beginning of a potential conversation. I meant that there are two options in a pure PvE environment: communication or ignoring. In a PvP environment there is a third option: combat. Sorry for the confusion.
In open mode that third option is always present. Chances are often low that the other CMDR will attack, but it's there and it influences the way somebody plays in open mode.
An "open" PvE mode would be nice. No PvP, lots of CMDRs to chat or work with - a big Coop mode. I think players would be more willing to talk to each other without the fear of getting attacked.
*) beside being docked - are there other situations where a player can't get attacked in open mode? Doesn't really matter as in most situations a player can get attacked in open mode.