Most people think that wires should be in conduit to protect the wire.
Although true, the main purpose is to give a way to flow massive amounts of electricity at the breaker that is energizing anything that shouldn’t be energized. This photo here, the wires can energize the fan and the fan will remain energized. There is no way to turn the breaker off and this is when houses can burn or people get hurt. Running wires in the fashion shown in this photo is just plain dangerous.