It is a space game though, and space is mostly empty. And the emptiness makes it feel larger. You still have the choice to go where the people are or travel with a group.
When Eve first came out I thought it would be pretty empty of players because there were so many systems. But even with a fraction of the player base they have now, players were just about everywhere. DU will be a bit different though because there won't be as many bottleneck points where players come together, but there will still be stargates and market hubs/cities.
Games like Elite Dangerous feel empty outside of the bubble because the millions of systems already exist in the game and you can travel to them, in DU it will just start with 1 system.
Games like NMS have NPC everywhere, but still feels lonely because it's all the same. I never felt like I was "far away" from anything.
If player-like NPC are put in DU I'd hope there would still be a way to find emptiness instead of seeing them everywhere. I'd prefer to only see NPC fauna on habitable planets, some maybe dangerous and most not very dangerous. Some optional pve gameplay could be created with them also.