One of those age-old ideas "the customer is always right" has always haunted service providers. It is not because service providers want to treat customers anything but nicely, but that the landscape of customer service has moved on from the last few decades, and today's world is much, much more sophisticated and complex.
The customer today is no longer as loyal as the customers of old. There are many more options to choose from. The economy is no longer robust and sustainable like the old days. There are much more political and sociological factors to consider on both the macro-economic and the micro-economic levels. Loyalty is increasingly transient and fleeting these days.
Therefore, to insist that you can always get your way as a paying customer, would also mean the service provider would have to look at you as a customer, and what you bring to the table. It is a partnership, not slavery. And as partnerships go, it must be an equitable, committed, and mutually beneficial relationship.
The service provider will do his utmost to serve your requirements and professionally, and certainly elevate that to a warm relationship with tenure. Note that tenure is important - you don't expect a provider to instantly treat you like royalty and know every little nuance of a need you have. That takes time, and that means you have to commit to this partnership and relationship over a long period of time.
From the perspective of a customer, the service provider would also expect equitable remuneration for services rendered and products delivered. If a customer trims remuneration until the service provider can no longer sustain the relationship, then there is no further partnership. If a customer makes unrealistic demands that are not equitable to remuneration, again, it will be difficult to expect such a relationship to last.
It is not impossible to have a perfectly nourished relationship and partnership between a service provider and a paying customer. It takes mutual agreement, mutually beneficial terms (that often means decent remuneration for the service provider on payment terms adhered to), and good manners and professionalism from both sides. And while no commercial relationship can be expected to last forever, both sides can make good on the relationship and treat it with mutual respect as long as it lasts.