The devs have stated there will be various activities and goals besides sightseeing, including resource gathering and combat. It's all optional, though. Apparently, you can be anything from an aggressive mercenary to a flat-out pacifist. That's part of the game's appeal for me.
Frankly, I've been wanting a game like this since I was a kid.[footnote]My adolescent self would have wanted it to be set in the Star Wars universe, but hey, beggars can't be choosers.[/footnote] While there have been great open-galaxy games like Elite 2 and Wing Commander: Privateer, they tend to focus more on combat and earning a profit than the pure, simple joy of exploration and discovery. After all, space is the final frontier.
The notion of exploring the (admittedly romanticized and scientifically inaccurate) cosmos and finding wonderous alien worlds strikes a chord with me. With a gorgeous art style and a mind-boggling 18,446,744,073,709,551,616 planets, No Man's Sky seems like it's quite capable of scratching that itch of mine.
I'm doing my best to curb my enthusiasm, of course. Plenty of game developers have promised the moon to players in the past to no avail. I fully realize that unforseen complications may end up toning the scale back, the procedural generation could result in same-y or borked planets, or the game may end up playing like a piece of shit. For now though, I can't help but be excited.