Why did Minecraft have a survival mode?
For a game that started out as a purely creative experience and is often still played as such, what does a survival mode bring to the table? The survival mode itself is honestly rather shallow compared to some of the myriad of survival exploration games that came after Minecraft. Combat is much more engaging in Terraria. The resource and health management aspect is much more challenging and focused in The Long Dark. You could argue that survival mode in Minecraft is its own experience, but I would argue that it actually enriches a creative experience. Having to go and collect limited resources to build with, having to watch your step around terrain hazards; these are things that teach you to appreciate the environment, and often, force you to build around it (or demolish it, if you like). In this way, a building becomes a base, exploration becomes expedition, and the seemingly at-odds gameplay of base-building and survival exploration are tied together and give each other new meaning.
Taking this perspective on why it helps building games to have survival modes also helps us understand why survival exploration games have base-building. In Terraria, the game encourages you to build up your base in order to house NPCs that help you progress through the adventure. In games like Subnautica and Astroneer, depleting oxygen/power bars encourage you to expand your base to expand your range of operations. On the other side of the spectrum, base-building mechanics in Starbound and Trove lack depth because they don’t relate to any other aspect of the game in a meaningful way, and while No Man’s Sky’s recent updates attempt to add base-building, they could easily end up just as disconnected.
On the other hand, Neither The Long Dark nor Cube World have base-building, and that’s probably fine. Not every game needs to have base-building. But it pays to consider how mechanics like power/oxygen bars, resource collection, base-building, and even just the ability to die interact with each other.