Not a good way to get repeat business

A lot of people find buying a car to be a stressful experience, what with all the pushy salesmen and credit checks and financing deals, but most customers don't have to put up with anything like this:

A 73-year-old car dealership owner has been sentenced to 10 years in prison for attacking a customer with a machete.

Robert "Jack" Parker, who must serve five years before he is eligible for parole, was convicted Wednesday of aggravated assault with a deadly weapon after a jury deliberated for less than two hours.

According to police, Gerald Davis had purchased a car from Time Auto Sales and went back to the dealership to pick up his license plates. Police said Davis, 53, and Parker began arguing and eventually Parker produced the machete.

Now, Parker's attorney argued that he pulled the machete in self-defense, but I guess the jury didn't buy that. My main question is why someone would have a machete at a car dealership.