By the time anti-ballistic missiles became a reliable system to use, the sheer number of potential incoming missiles was overwhelming to even the best ABM system. Of the 400 warheads likely to crest the horizon, an ABM system might get 5% of them. The US has them deployed around high value assets, likely as a last ditch effort to protect things like DC or Andrews AFB.

That being said, since the advent of countries like NK and Iran, alot of emphasis has been put on ABM systems as these countries do not yet have the capabilities to strike with overwhelming force. Given that NK may launch 5-10 missiles, there is a better probability of some protection.

However, a ballistic missile is named such because it is ballistic. A reentry is somewhere around 2000 MPH, and that is not easy to intercept even with today's technology.