They assume that young people won’t start if they know how bad smoking is. Sometime, health organizations may want to change people's behavior getting them to exercise more, for example.
However, advertising is more often used by industry to sell things. A company’s income depends on how much money it makes by selling its products and services. These days, the trend is for companies to advertise their brand. A brand is a mark, a name, or a label that stands for a company’s products or services. In the past, a clothing company would advertise a coat or clothing.