Someone has to advertise.
Someone has to publicize.

Shameless self-promotion is the epicenter of the music business. You can’t talk to anyone unless you’re someone and image is everything. Advertisers generate image for dollars through ads in TV, radio, newspaper, internet, etc… Publicists generate image for free through word of mouth, street teams, newspaper articles and publicized events. Also included in this broad category are those who represent another: talent or booking agents, personal or business managers, promoters, attorneys and the like. These are the people that make the connections of the other 3Ps happen.