Is not it a contradiction that an 18 year old can not buy whiskey but they can do movies and go to war?

Do you think we should write our law makers at federal level, state and city level to make it illegal to appear in movies before age 21? Let us get real, the average 18 year old is not mature enough to consider the long term consequences of being a " star." Our laws will not allow them to buy strong alcoholic drinks or ciggarettes. is not this a blatant contradiction? Many of our law makers see them selves as moral or Christian or some other faith that says is wrong but yet it appears none has the guts to take on the industry. NOT EVEN ONE. Why?