Why do they make microwaves beep in 30-second intervals after the food is done?

One of the features I cannot understand is that every microwave I have owned would beep in 30-second intervals when the food is done, indefinitely, until you open the door. What is the point of this? Are they worried you are going to forget about the food? There is already a mechanism built into every human for that, and this is called the sense of hunger. So why do they make it beep?

This beeping thing is highly irritating, because often you want to leave the food in the microwave so that it will cool. Also, sometimes you are working on something and don't want to get the food out right now. I hate the beeping microwave thing. I wish there was a way to make it turn it off, but none of the microwaves seem to have this option. Do you enjoy this beeping behavior?