Some young people, at age 15, may very well be mature enough to drive a car, while others, even at age 17, are not. Yet anyone who has tried to discuss driving rules with a teenager understands this desire to argue, at all costs, along objective lines rather than get into a debate on the intrinsic qualities of the individual. It is hard to say whether a young adult does or does not know his limits well enough to consume alcohol, or whether he can properly assess the risk of tobacco addiction in deciding whether or not to smoke. We use age as the barometer because it's easy. While for children and young adults, birthdays are associated with positive notions such as being able to take part in more activities and having more rights and responsibilities, as time passes, the reverse becomes true.
Birthdays eventually come to be associated with declining abilities and skills.
The law follows suit, and associates messages of incapacity with advancing years. According to some provinces and under federal legislation, for example, mandatory retirement at age 65 is still tolerated. Other provisions have less of an effect on people, but also rely on age as the barometer. People over age 60 do not have to assist at the scene of a fire. Those over age 70 cannot hold certain jobs in some federal agencies.