Even when the synapse is at the axon hillock the channels activated by the EPSP rapidly become refractory

Most synapses are at the cell body which also receives inhibitory input to cancel the EPSP

Even when the synapse is at the axon hillock the EPSP is too short-lasting an event to allow summation

Most synapses are at the dendrites and there are no voltage-gated Na⁺ channels at the dendrites to produce an AP

Most synapses are at the dendrites and there is too much loss of current from an EPSP by the time it reaches the axon hillock