I think the biggest clue for me was the game releasing with a free dedicated server app, plus the design decision of letting you move characters (and worlds) freely between sp and mp.

Adding a second player doesn't really double your resource needs.
You don't need bigger bases, one person can gather or farm while the other's offline, and things like mining trips are far more efficient with a spotter and guard. Creatures get a small buff when facing two players but it's no match for backstab.