I'm not sure I understand that answer.  When you are flying around and you approach a class B,C,D airspace do you not call the tower for entry?
 
I understand the class B maybe a bit more complex but is it not a start? Class C is 90% of the time tower controlled.
Displaying the main tower freq for the B,C,D airspace it would be a start to display the tower freq.
 
 
Does ifly really alert you before entering class A?