In fast switching applications like switching regulators, the body diode's reverse recovery time may be too long but they make power MOSFETs with pretty fast body diodes now. The lower forward voltage drop of the schottky diode prevents the body diode from turning on. An external schottky freewheeling diode in parallel with the power MOSFET might be used if an inductive load is switched back on before the magnetizing current decays to prevent the reverse recovery time of the body diode from causing excessive shoot through current. There is usually nothing wrong with using the body diode of a power MOSFET as a freewheeling diode and it has the same voltage and current specifications as the power MOSFET itself. Some are manufactured with this diode deliberately added and bipolar darlington transistors intended for switching applications often include it. The situation is different with bipolar transistors for the reason you identify they do not include a built in freewheeling diode by default.
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