I don't think the purpose of the EVSE is to prevent problems if the EV or on-board charger malfunctions. At the other end of the spectrum, however are those who don't understand why a traditional NEMA dryer or range outlet is not a suitable standard for EV recharging.
What does an EVSE do?
1. It automatically enforces the recommended practice of de-energizing the power before the current carrying contacts break. With NEMA type RV outlets this must be done manually.
2. It contains a GFCI circuit to shut off power if unsafe ground leakage occurs. Most dryer and range outlets don't have GFCI protection; it is starting to become more common on RV outlets.
3. It generates a pilot signal to automatically tell the EV charger how much current it can draw without tripping the breaker. This allows a flexible, universal connector which will work in many situations, If the car used a NEMA plug, there would be no automatic way to adjust the charge rate to the circuit capacity.
4. It prevents the EV from back-feeding into the power panel. Eventually, this will change when V2G becomes a reality, but until those safety standards are set, the EVSE is a gatekeeper which prevents it.