When writing a Torah the letters שעטנזגצ (as well as the "final" letters, ן and ץ) have "crowns" on top of the letters.
What is the purpose of these crowns and why were these specific letters chosen as the ones to have them?
(I am aware of these letters as being the ones with the crowns based on Ashkenaz tradition. If there is another tradition that uses other letters, please indicate this in your answer.)