Why is this petrol station so big? I could park 2 tanks between the petrol pumps.

Caseys has gas stations in extremely small towns so something they have to space the pumps for is farmers coming to fill up their tractors. It is also common practice 'round here to put 3 car widths of space between pumps to allow vehicles to drive between those that are filling. Obviously in larger cities where land is a premium they’ll have fewer pumps closer together