4x4 isn’t even a correct term. That name came from WWII vehicles with a 4’x4’ cargo space.
They happened to be four wheel drive but that’s not what “4x4” means.
The best argument for 4WD I’ve witnessed was driving over the pass in the snow one day.
A guy in a 2WD pickup suddenly spun out and hit the wall. It was because we were all on the throttle to climb uphill, but he broke traction and spun. Everyone else around was in 4WD and didn’t.
While it’s a side benefit, the low-range gears in a 4WD transfer case are a big advantage in lots of situations. 4WD trucks have tons of advantages. 2WD trucks are a little cheaper.
That’s basically it.