Problem is, right now the multi-player aspect of this game is very NON-obvious and sometimes even hidden.
First, other players you only spot by their icon on the screen which is a "non" filled out as opposed to "filled" out dot on the radar.
Most players are actually in supercruise (I see quite a lot when cruising) but you cannot really interact with them while cruising, interdiction etc. doesn't work.
The chat feature of the game is very non-obvious and many might even not bother or know how to chat.
There *IS* some PvP action going on, but you need to go certain places like freeport etc. Many of those places I myself don't even know about, its stuff you have to find out from reading on forums etc.
Edit: It might also be true that the game really is not that known in the US yet. That means that at times when it's early morning or whatever non-gamer time here but high-time in the US, less people are on.
Edit2: "If I say something on Eranin"
I don't even know whether the chat works like this, eg. that everyone on/near Eranin would actually see what you say. I don't think there is such a "trade chat" or "global chat" feature yet, I have never seen ANYONE.
If so, this would be an URGENT requirement to get this game more feeling "alive". Any multiplayer game has a trade chat, global chat etc.. I am sure these features are still coming. Remember, it's Beta. (As I pointed out above, the chat how it's implemented right now is very..underwhelming. This is important since communication is key for a good multiplayer experience, for the feel that you're really playing with others).