What you have here is a vicious circle (no pun intended):
Folks learn to fly and are scared stiff of stalling by bar stories and badly demonstrated stall lessons. Spinning is then the subject of even more scary stories and is therefore either not covered or poorly taught including horribly alarming flick entry spins.
These folks become instructors and perpetuate the myths and apprehensions.
In summary, it is partially caused by poor instrucional technique and partially by poor spinning qualities of training aircraft which require a rather uncomfortable flick entry to actually enter a spin.
Really and truely, however, a good lengthy set of stalling sessions (preferrably with the stall warning CB pulled if possible) will do much to improve student confidence and knowledge of stalling.
Students are made victims of the 'recover at the first symptom' approach to stalling. First we should teach all about stalling, then we should teach minimum height loss etc.