Respectfully, that’s not the case. The heating elements always have current supplied to them, but the circuit is open until you complete it by pressing the moving segment down. When you use a metal tool and accidentally touch the side, you complete the circuit.
This is also how people can kill themselves by putting a toaster into a bathtub while they are in it.
You don’t need a switch if you are bypassing it with a knife or other conductive object, that’s what I’m trying to tell you. A toaster has literally no protection - if you complete the circuit in any way (the intended way or not), the entire path becomes electrified.