A) They develop their finnage to their maximum potential. In order to achieve the full "halfmoon" look, they must actively stretch the membrane between the rays.
B) They can flare on command. Flaring on command is *very* important for showing. When the judge removes the card, the bettas are expected to flare and display. It is very difficult to judge a betta that is not displaying properly, and it is a severe fault if they have such poor deportment.