True enough that many restaurants and service-oriented positions are moving away from cash. The security of not having young people, or anyone, handle cash is replaced with card processing fees. It is a trade-off.

Currently, many fast-food service workers earn $15+ per hour. Restaurant service workers somehow earn far less. Unless, we go the route of regulating those wages, various locations still have the right to structure as best suits them. Therein lies the discrepancy.