Unfortunately, that adage had an implied responsibility by the customer to make an honest attempt to do the right thing ... in modern culture, responsibility seems to be a forgotten concept.
An example of how customer behavior forced me to change my own policies ... I train to higher than minimum standards. My approach has always been that we set course objectives ... and the class is over when the objectives have been met. For this reason, there is no "minimum" number of dives. I've been known to do as many as 10 dives for OW ... and 14 for one particular student in AOW. And I'm happy to provide that service, because it turns out more competent, confident divers. A side-effect of that policy is that my class schedules tend to be a bit flexible ... and I encourage students to do the responsible thing and if somethign isn't feeling right, call the dive.
Last year that got translated by one particular pair of students as the right to call me the morning of our scheduled dives and tell me they were stuffed up ... or had a headache ... or their ears were bothering them ... and reschedule the dive. Often this would happen about the time I was showing up at the dive site ... or in one case, just after I had gone out and set up the navigation course. In total they rescheduled 11 times ... costing me not just travel expenses, but also the ability to have used those days for other activities.
I finally had to tell them that any further cancellations would result in a $50 rescheduling fee. And now that's written into my policy. I can choose to waive it, if I feel the cancellation is for a legitimate reason. But the point is that if inconveniencing someone you're getting a service from doesn't cost you anything, there will always be a certain percentage of people who won't think twice about it.
The reality is that the customer isn't always right ... because, as my course director once told me when I was training to become an instructor ... if you don't put a value on your time and services, neither will they.
If you want to blame someone for a decline in services that vendors offer their customers, blame that percentage of people who will always seek a way to "game" the service, costing the vendor money. No one you buy a product or service from can afford to just give away their time and inventory for free. Those days are gone forever. They went away when so many people in this country developed the attitude that somehow, someone else owes them something ...
... Bob (Grateful Diver)