As mentioned in earlier threads, the exit swirl (i.e. vortex around the engine certerline) is a significant factor. A simple prop operating in the free airstream, while doing its job of accelerating the air, imparts a rotation too.
Said vortex represents an investment of energy, but does no useful work in creating thrust. It's an energy loss.
But there are ways of recovering this energy. One is to use counterrotating (umm - contrarotating...) props, one behind the other. The aft prop will redirect the vortex into more or less straight flow.
The turbofan uses a row of fixed stator vanes behind the fan rotor to do the same job. Since the flowpath between adjacent vane airfoils is divergent, the airflow is slowed as well as redirected, so now its static pressure within the fan duct is increased. Finally, this higher-pressure air is forced through a nozzle to accelerate it to a speed where it can propel an aircraft efficiently at high subsonic cruise speed.