An E Stop is to put the system to a safe state. It is intended to be used even by the uninformed/untrained, yes, but that doesn't mean that it can't be designed to do complex/intelligent things.
For MACHINE safety, safe state usually means stop as fast as possible then cut power. Sometimes, though, you need a coast stop rather than a ramp stop.
For PROCESS safety, there are very different standards. Quite often the uncontrolled process is a larger hazard than whatever local thing they want to estop. You may need to prevent the building from exploding to protect the individuals in it. Often times this means there is redundancy to the control system, but sometimes it means a valve to either dump the contents of a tank or prevent anything else from flowing.