You’re in the business to make money. That’s it. Why would you not always offer every way possible to earn that money? We may someday be a cashless society, but that’s a long ways off. Nearly 45% of my revenue at my washes are still cash and
coin. These earnings are worth more as well since they come workout credit fees. In this business (self service) keep all options available to earn, never give away free services (vacs, air guns etc), and maintain a tidy ship with a well run fully optioned site and your bank account and customer count will grow leaps and bounds. Again, in the end it’s all about gross earnings.