Because they were told that in a John Wayne movie. "Never apologize. It shows weakness". Such bullsh** crap. Only the mental defects think that.
In order to apologize, one has to set aside their pride; in other words, they have to humble themselves. People see humility as weakness, therefore apologizing is a sign of weakness as well. Any fool can act tough. However, it takes a truly strong person to be humble.
When pride comes, disgrace follows; but with humility comes wisdom.