A few people who could not understand Minecraft are in this thread, ey?
No Man's Sky is based around the concept of 70's/80's Sci Fi, particularly Dune. The main emphasis is just the experience, in the same way as Journey played out. For me, it holds more appeal than Star Citizen, in all honesty. The premise of game universe, so vast that the human mind can not truely comprehend the scale, and the freedom to essentially go any where, with very little limitation on doing so.
The question why? does not really work with this game. Much like in a game like Minecraft, the elements and core of the game, just are. If you are not overly interested in the game, I would still suggest looking into how they are actually making it, not for the sake of converting you, just that the process is rather interesting. The game is almost entirely procedural, and considering that the game has been made of a team of only 10-11 people, the feat is quite impressive.
In the end though, to each their own, and if this is not your cup of tea, then simply go else where for your coffee.
Edit: One last note, technically there is no end to Star Citizen. It has no true objective for you to achieve. In the end the game is simply what you make of it. The same can be considered here, just that unlike Star Citizen, it is kept vague. They do not want you to know how to do everything, or what you can and cannot do. It is apart of the expeience, to figure things out. I suppose it is this that may be the cause of the confusion as to what the game is, or maybe people generally prefer to be told what to do, prior to engaging in such activites. Strange that, considering the popularity of exploration for Star Citizen...