Don't know about you, but I have a habit of putting the oven timer on, leaving the kitchen, then becoming distracted, only to realize that the buzzer has gone off, but I didn't hear it, until something begins to gnaw at me.
Then I realize that the electric timer has been beeping every 30 seconds to remind me, "Beep! Beep! You have forgotten to pull me out of the oven!" So, I jump up and dash in there hoping I have not ruined what I was baking.
Problem solved. Now I take my new timer with me as back-up. It has a magnet on the back, too, so you can attach it to the fridge.
B