@hansw There is a coordination problem between producers and consumers. Consumers have a problem to be solved and producers are attempting to profit by solving it. In principle, this is usually beneficial to *both parties* — I would be made better off by most of my purchases even at much higher prices (and the sellers are making money on everything I buy).
In principle, advertising is a mechanism for telling people that there are solutions to their problems (or that the existing solutions have improved, or prices have changed, etc).
@hansw The promise of targeted advertising is excellent: An oracle knows every product that is available and perfectly predicts your current and future desires, then tells you about things it knows you want.
Everyone is happy. Consumers get only information about what they want, producers know the exact size of their market and capture it fully (and can adjust what they produce if it is not profitable to produce for the market).
In practice, such an oracle doesn't exist and there are all kinds of unfortunate dynamics in the advertising market that makes it so that people generally don't like ads, plus all kinds of "off-target" effects.