Because its soo formal. like i have i a friend called isabella and she kills anyone that call her that IT IS BELLLA! like ... i find alot of isabellas are like that.. and they like it.. its nice and short. jsut bella.
Because she is stupid. Isabella is beautiful, it was a name of queen of Spain and many other remarkable women, so I guess it's actually good that they don't call her like that, since she is pathetic excuse for a woman