Applications that require very large switch currents (i.e. >10A) will most likely use external switching MOSFETs in combination with a Buck or a Boost controller.
These configurations are often used in power converters with output powers larger than 25W
Controllers with external MOSFETs are also used in circuits that have very high switching voltage, for example in applications that are powered from the AC line voltage (Flyback controllers and PFC controllers).