It is a misconception that the circuit breaker is designed to protect appliances in a home. They are thermal devices that are designed to heat up to the limits of the wire’s current carrying capacity. When they get to the safe upper limit they expand to the point the spring releases inside and opens the circuit like a re-setable switch.
Not to be confused with fuses which are one time devices designed for the same purpose. They have a small wire designed to melt at the upper limit. So in conclusion they protect the wire from getting too hot and starting a fire.
A side effect is they protect the appliance from current surges. But they are rated at the wire current capacity.
From an electrical power source, electricity flows down a source wire to a load that limits the current flowing in the wires, and back along a return wire.
But if the source and returns wires connect causing a “short” circuit, the current increases massively to the point that the wires overheat and melt at 1085 °C, or even vaporize around 2562 °C, and then your building burns down.
To prevent this you need to stop the current flowing around the short circuit, which is what a circuit breaker does.
Circuit Breakers are used in almost every flat, house, building, campus, factory, basically, any place that has electric appliances. It is a device used to protect the electric appliances from any case of over-current, overload, or short-circuit.
In other words, everything (refrigerator, AC, kettle, toaster,..) has a certain tolerance (rating), if you exceed that limit it will blow. Although nowadays most electric appliances should have the same kind of protection, that the circuit breakers offer, inside them but that depends on the quality.
For example, if you get a cheap microwave it will definitely not have overcurrent protection 1. because its cheap, 2. to make force you to buy another one
Now take this idea on a larger scale, a university campus, for example, each classroom (which has lights, computer, projector,..)or lab (which has electric powered scientific equipment ) has separate circuit breakers where they are usually grouped in a box, and these boxes are usually grouped in something bigger (switchgear).
Imagine if there wasn’t a circuit breaker and for whatever reason, high current passes to a certain device in the lab exceeding its limits(rating) that will damage the device and might even affect other devices connected on the same network. Also, high current or a short circuit somewhere can sometimes cause a fire.
So, why risk all that, just use a circuit breaker.