You could be a tough guy and still care about the development of your derriere by drinking a beer that has less calories. The beer was a hit, and soon every major and minor brewery had their own version, taking away part of Miller's share of the light beer market and the associated economic profits. Recently we have seen the same development in the microbrew market with the major brands releasing their own, in appearance, microbrew. The easiest way for a firm to compete is with price - charge less than the other firms for a quality product and take significant chunks of their market share. But cutting prices often leads to lower profits.
Advertising is a way for firms to avoid serious price competition - look at the auto industry.
An even better way for a firm to avoid price competition is to cooperate or directly collude with your competitors. Note how two gasoline stations located across the street from each other charge an identical price. It would be easy for one station to undercut its competitor by a few cents and grab an increased market share. But the station owner knows that if he cuts his prices, the station across the street will match the price cuts and they will both end off with lower revenues and only the consumer will gain. Direct collusion between businesses to restrict competition in the United States is illegal, but it certainly happens.