Since the event horizon is defined as the boundary within reach the escape velocity is greater than the speed of light, and escape velocity is the speed required for that object to reach infinity away from that point, why can't light escape the event horizon even if it doesn't reach infinity away from it? 
For example considering a photon on the event horizon with velocity c, the change in potential energy to move say 1m across it, as opposed to infinity away from it, would be smaller than it's kinetic energy?