I'd say there has to be random risk for it to be a survival game. Otherwise the player has complete control and then its a building sim. Getting rewards such as bronze/iron, it they are just given with no risk, gets pretty boring.

As near as I can tell though, you only get raided while in or very near a base. And it has to have enough campfires,workbenches, torches and or a bed to qualify as a base. No idea what those parameters are. Theoretically, one could just be a nomad and stay in pre-made shacks and you shouldn't see a raid then. JUst the normal traffic from spawns/nests/body piles etc....