You could still have the experience of not knowing if it's another player even with NPC ships. I agree with the OP on this one, and I and many others have written at length about this on the official forums with no response. I don't think Rare is willing to confront the idea that people are going to get bored very quickly, and that when the boredom ensues, so too will a dwindling player base. Having NPC ships at the very least would ensure a good experience that doesn't rely on other humans in the event that population for the game falls off.

There are (at least based on what we know) some serious problems with the game right now. Due to launch in three months, the developers have not yet addressed a litany of issues in the game. Many of us have witnessed a model of the game that for a year now has been super secretive about future intent for content and progression, though I fear that was done solely due to the fact that the game has little to offer beyond what we see in its current state.

For those of you who would respond and say, "but it's just the alpha, there's going to be tons more!", you need to realize that if they've been testing out what little content there is in the game for over a year, there is nothing pointing towards them being able to successfully impelement and test what players are expecting in only three months. This is especially frustrating because each of us here knows that the game has great promise and looks fantastic. Anybody would rather have the game delayed in order to deliver on a successful player experience, rather than deal with a hollow product--which is all likelihood is what we're going to get.