Some of it's necessity when I sent a few thousand long tail lambs to the Haj it was explained to me.
Every Muslim must visit Mecca and when they do they must give a pure lamb to the needy, hence no chopping off the tail. Obviously they cant all go with a lamb under their arm so they pay a fee to the Saudi Govt who then buy shiploads of lambs. These ships are then sent to the poor Muslim country of choice where presumably the locals who don't own refrigerators or big screen TV's buy them at a subsidised price and ritually slaughter them. The live sheep exporting countries have tried to train locals and teach them that a non stressed animal tastes better but its been a waste of time because we only have influence while were sending animals there.