Comment by njovin

Most frequently the actions/evidence that lead to a crash would not be captured on airport-located cameras. The holes in the swiss cheese usually start lining up either in the maintenance hangar, en route, or in the briefing room, not on the runway.

The NTSB (and many of their non-US counterparts) are incredibly adept at accident investigation using debris, black boxes and CVRs. Even in cases where the black boxes are damaged and video evidence is available, the video evidence is usually not so helpful as to be able to determine a root cause.

If you take into account that the cameras would be mostly useless in low-light or poor visibility conditions, and the costs associated with maintaining a nationwide network of high-res cameras that cover all runways at all major commercial airports (and ensures their lines of sight and operation through the never-ending renovations going on at these airports), I'm not sure that the benefits of having the cameras make sense.