Please don't make it more complicated than it really is. I've paid higher rates and cab fares for late-night appointments, even with transit still running, just because it was going to be more comfortable for the provider to get back home in that way, for accomodating coming see me late night.
Service providers are free to charge a higher rate to cover business-related costs or assume them. They also have the freedom to decline a request for an appointment if the resulting outcome is not going to be as profitable for business.
Nobody is putting a gun to their heads forcing them to take every single request they receive, nor apply the same rate to everyone no matter the circumstances. It's a free market.