Style().configure don't works for all widgets

[Luis Marzulli]

Hi
Why 

ttk.Style().configure(".", font=('Courier New', 30, "bold"))

works for Button and Label widgets (and maybe others) and don't works for Entry widget?

Example in Python 3:
from tkinter import *
from tkinter import ttk
from tkinter import font

root = Tk()
ttk.Style().configure(".", font=('Courier New', 30, "bold"))

ttk.Entry(root).grid() # don't works
ttk.Label(root, text="my text").grid() # works OK
ttk.Button(root, text="some text").grid() # works OK

root.mainloop()

Thank you