Jet blast walls are a thing, too.
Also lots of trees. The number of airports with runway runoff fields is really quite small. Cities tend to grow around airports. Pick a random major airport, go into Google Maps “Satellite” view, and look at the ends of some runways. Start with, say, DCA.
At least in North America, there are rules about how much flat ground there is supposed to be past the end of the runway.
But most of the existing airports don’t meet them, and they were all grandfathered in.
In a lot of cases you overshoot you end up in the ocean, but that is better than hitting a bunker that creates nonsurvivable decelerations.
Every airport has beacons and instruments at the end of the runways. But I’ve never seen them be built inside a concrete bunker.
The FAA has specific regulations for the required lengths of the Runway Protection Zone at ends of the runways. These are based on the size of the airplanes that the airport is rated from Category A (small general aircraft) to Category D (large commercial jet aircraft).
All federally registered airports are eligible for FAA safety grants to make improvements identified on their annual certification inspections.
Look at Midway.