@Melonlity -- I see what you mean, but I do believe defamation lawyers in large cities could find enough business to specialize in that field.
But, isn't that always the way? When you get to rural areas, you will find a lot less specialized attorneys and a lot more general practice attorneys. They have to run general practices to survive.
Lawyers in big cities have the ability to specialize while those in small towns usually don't. That's just the way it is.