>>15417395
Because they forget that the fundamental purpose of Procedural Generation is merely to give you different and unknown start conditions, it serves to gameplay purpose after that.
Gameplay must come from the interactions of every element that ProcGen puts in your world, meaning the world and actors in the game cannot be static in nature.
This is the tiny detail that gives ProcGen a really bad reputation, despite being quite a nice starting point on paper. Devs create a literally unique world for everyone so you can do different things in it than anyeone else.
However, the rest of the gameplay and NPCs will behave as if they were in a linear game with handcrafted levels instead. There'll be little interactions and reactivity from them or the world itself and the player will end up doing the same thing every single time despite having a different starting condition.
>No Man's Sky
There are rival factions in that game and friendly ones as well. A good sandbox game would give you the option to join one, inheriting it's enemies as well or let you start your own and use diplomacy.
Afterwards, the point of the game would be the competition between factions, each wanting to progress to the center of the galaxy and needing resources harvested from planets that they must control.
If the factions themselves were active and took planets from one another, had an economy and diplomacy that created trade routes and truces or alliances and the player could also join in on all of this, you'd have a purpose for all the shit you often do in these games.
Build a base because it will mine\farm resources sent to a station and traded across the galaxy or used to strengthen your fleet.
Explore planets to find newer and better resources to use or more space for the civilian population of your faction.
You can't have all the required resources to finish the game without butting heads with other factions so wars and alliances are inevitable.
You'll go back to previous planets to defend them or change their structures as well, maybe even having to retake them.
>Starbound
Here it's even simpler and they could take a queue from how Terraforming works in Endless Space.
You have a bunch of tiered planets, the lower tier being more hospitable while the later ones are much harder to survive in.
Put crops\minerals available on each planet based on it's tiers so the first ones will have the simplest most common plants and ores but in larger amounts, while the later ones will have rare but scarce ones.
Tie in the population of settlements in the planet to it's tier, lower tiers having higher populations.
Now you need all tiers since the first ones makes the bulk of food and tools you need for everyone, the medium tier makes all the upgrades you need for settlements\ships and the later ones make the unique powerfull gear\equipment.
In order to finish the game, a player would need to colonize and build something like 10 tier 1-2 planets, 5 tier 3-4 planets and 2-3 tier 5 planets while setting logistics\trade routes between space station to keep them stocked as well as any planet below them.
At this point you can visit planets to upgrade and optimize them, maybe have events where they are attacked, but most of your supplies are delivered to space stations, you restock from there and move on to the next adventure.