Sure there are lots of reasons for rwy overruns but for the most part they all result from unstable approaches and long landings.
I'd be willing to bet that most crews KNOW--as they continue their unstable approach and long landing--that it's a poor decision. And yet, continue they do.
Therefore my conclusion is, there is a BIG reluctance to abandon a poorly managed approach. In other words, this is a psychological question.
Why are crews so reluctant to go around and try again? Answer that question are there is your solution.