You call everybody by title *'Sir'*. You know what is meant by word *'Sir'*..? *'Slave I Remain (SIR)*' The British during their rule wanted all Indians to address them as *'Sir'*. Even after 69 years of independence, we still keep calling everyone *'Sir'*. Even American President is addressed 'Mr. President', not 'Sir' .
MANY PEOPLE DO NOT KNOW THE REAL MEANING OF THE WORD AND THINK IT IS AN ADDRESS WITH RESPECT.