Dogs communicate with each other through body language, but most people do not understand or look closely at their dog's canine body language. When a dog continually tries to communicate and is not understood, they can escalate to things that do work, and work quickly: growling... and then biting. If we scold them for growling, biting will be even more probable.
These behaviors aren't terrible in dog/dog communication. Dogs growl at each other to communicate things... and it isn't a deal breaker in their relationship. They'll even get into scuffles, and the friendship picks up a few minutes later. But biting humans is a no no, and millions of dogs a year are euthanized for biting humans.