I can't understand why anyone needs a warning buzzer to take their keys with them.

Why would you not take your keys out of the ignition and take them with you?

Why would leave the headlights on? If your headlights are on it must be dark, you should be able to see it

I always know when I have a door ajar, I don't need a chime or warning light to tell me

Maybe I'm just more observant