Perhaps they will charge extra money to charge a car at the full speed the car is capable of and hobble charging speed for a lower price.
This would tie up their charging infrastructure and space for a longer time, making less money. Gas stations & charging venues are usually space-constrained because they're located on expensive real estate. Their goal is to maximize revenue and throughput in small spaces.
Makes me wonder what benefits there are to convenience store sales in states where "full service" is required.