sir, Madam and Miss

涂于德

May I carry your cases for you, Madam?

Excuse me, Miss, could you tell me the way to the station?


Would you like to see the menu, sir?
\"Did you hear what I said?\" \"Yes, sir.\"


I have no idea why \"Madam\" and \"Miss\" are captalized here
while the initial letter of \"sir\" is small here?