Microwave is usually 900W while a Non-US kettle can do 3000W on a standard 240V 16A connection so it boils water more than 3x faster.
Very convenient for serving tea and instant coffee and also useful for cooking potatoes, veggies, rice, pasta by boiling water first before pouring it into a pot for a quick start.



Imagine if we could have a 3phase kettle with 3x32A for 22kW. It would in theory boil 1L in 15s.