According to the Patriot Ledger from Oct 7, 1976, p. 17, the Town Counsel discovered that self-service station owners were planning to throw out the repair side of gas stations turning them into "back-door monopolies" on the part of the oil companies. This would deny gas station lessors of repair income. So the town decided to use zoning to prevent self-service gas stations. I am assuming this is the rule to this day.