Why do companies advertise their products?

Who knows where it started .Sometime some manufacturer/merchant realised that if they got to stand out in the market the exposure would attract more sales.If you gain more sales in a given market, others are losing sales.To regain market share the remainder of the suppliers must do likewise.

In my humble opinion they made expensive rods for their own backs.Most,if not all, people in business now know that probably half their AD. budget is wasted,the problem being which half? Second to that,no one person is going to risk cutting out advertising alone in the market for obvious reasons.

This is an opinion only and since it was more of a philosophical question I have tried to answer in kind