If your colony is close to collapsing, you have a chance for a “Man in Black” event where a stranger in black comes in and, hopefully, turns it all around.
But what if the MiB doesn’t trigger? Hell, what if they’re a pacifist pyromaniac with a meth addiction who wandered into a mass of cannibal sex slavers having a rave over the ashes and dies?
Someone will eventually come. It might take in-game years, but eventually, a pawn will come and want to make those ruins home. You can try to rebuild.
Admittedly, it can be quicker to just call it done and roll up a fresh colony over watching the seasons pass, but I like how even a complete loss doesn’t mean the story is done.