How are these not alike?

 I went to the dentist across Hiway 76 a couple years ago because a crown had a hole in it. When it was finished I was in for about $5,000.00. The practice was taken over by Riverside Dental so I decided to try again since I had a crown come off during our last board meeting of all times. I set the appointment telling them all I wanted was the crown replaced on the tooth. They are very nice people, as were their predecessors. The appointment was set and I came in to have the crown set back in place. I was told to get in the chair for exam and x-rays. I told them all I wanted to have was the crown put back, no other dental work. They refused without the exam and X-rays so I left. I was in no pain anyway so I planned to go elsewhere.
 Think about this. Let's say you set an appointment for an oil change. You arrive and are told you can only have an oil change after they connect your motor to the diagnostic machine and charge for that to be sure the engine is in good shape. Laughable, right? What the heck is going on with these people? You would never go for the second example but the first is accepted practice?  I don't get it....
Ken