It does not matter if you drive an automatic or manual transmission, or if you park on a flat road or up a hill.
Your emergency brake is meant to prevent your car from an emergency situation, and to be honest, not all emergencies happen in your presence.
This means that every time you are about to put your vehicle into park, you should first put your emergency brake on.
This will help keep your vehicle in place in case another vehicle hits your car, if there is a storm or any other unforeseeable emergency occurs.
Regardless of whether there is an issue you can see or not, you can be proactive if something were to happen when you step away.
So put it into practice and put your emergency brake on before you put your vehicle into park and keep your vehicle safe!