U/A certification not mandatory for films with smoking scenes

A question on my mind :

A hero puffs away, while a marquee rolls saying "Cigarette smoking is injurious to health"
What is a kid supposed to believe? His favorite hero puffing away stylishly OR a rolling text. May be the kid also gets to listen to 30 sec ad at the beginning, middle (Who stays after Interval to listen to an 'ad') and ponder "If smoking is bad and my favourite actor is good (Now-a-days Heroes are also playing shades of grey But mostly 'good grey' we can safely assume ) then why is he smoking?".

I guess pondering on such grand matters of being would help our precocious young buds to grow taller, sharper, stronger (by smoking?? oops!).

An interesting story comes to mind:
Sir Alex was a famous Hollywood star. He was approached by a liquor company to promote their brand. Coincidentally, he also drank the same brand But he politely declined. Thinking the money wasn't enough the manufacturer approached him doubling his offer. Sir Alex replied "It is not that I do not drink this brand, Or your offer is not good. It is just that Liquor consumption is not healthy and addictive So I prefer to drink in the privacy of my house, I can't share this addiction with my fans."

Detractors would argue : Smoking onscreen is a matter of personal preference. But then if it is so, why do we rate movies as U, U/A, A in first place? To my mind the only reason for rating is kids cannot make informed choices in case of Cinema and You gotta admit Cinematic charm is strong on kids, hence employed in ads to influence opinions.

P.S. Comments invited :)