Originally Posted by LoneyPie
I learnt that the reason was similar to what djpil earlier said.........
The 500' is there to give you time to recover if you were to get into ...an incipient spin.
From what I've seen with instructor students 500 ft is not enough. One comment in the debrief - "Does it often do that?" "Nope, generally only once in your lifetime because if that happened turning final you would have hit the ground." The young lads generally swear at me once they realise that what they took for a clearing turn prior to a routine stall exercise had suddenly turned into the exercise that I'd briefed. Not uncommon to go around twice in the Cessna 150/152 before they manage to stop it.
I recall that the PPL/GFPT test form used to have a climbing, turning stall on it but removed now! I can remember doing it in my RPPL test many years ago. Some-one told me that it was not within flight manual limitations of the trainers - can't believe that. Be good for everyone to experience a stall from a skidding turn.