I found this NYTimes article from 1982 but I don’t think it really answers the question:
Nearly 1,250 stations and 100 distributors upstate have been affected by the departure of Shell in 1977, Texaco in 1979 and the announcements by Exxon and Gulf that they would leave next year, according to the New York State Association of Service Stations; the group represents the owners of the state’s 8,500 gasoline stations. Some blame an oil company ”conspiracy,” and others the taxes on oil companies in New York, but neither theory can be confirmed and neither makes gasoline any easier to find.
The stations’ problems – declining demand and declining prices for gasoline – plague the oil companies, too, their executives say. ”There’s nothing wrong with upstate New York – it’s the overall, general conditions,” said W. Kirk Vogeley, a spokesman for the Gulf Refining and Marketing Company in Houston, a division of the Gulf Oil Corporation.
I recently drove from central New Hampshire to Pittsburgh via Albany and then Buffalo. I fairly saw an Exxon and never saw a Shell, BP, Chevron or Texaco station. Every gas-station was a local off-brand gasoline and here I am in a performance 1.2 Liter motorcycle that’s fuel injected and in need of quality fuel.
If you do a search on Shell’s website for gas stations in New York, everything upstate is completely barren until you get to Toronto where Shell has a big Canadian presence. I’ve been exclusively using Shell 93 Nitro+ for the last 2 years in my vehicles and it was a bummer to have to use non-name low-tier gas for this trip.