Denying your child medical treatment

is something I don't understand. Okay, I am not a parent. Yes, I have had responsibility for younger relatives, the children I taught, children for whom I have been the babysitter or childminder, and the Whirlwind of course.
If any of them had needed medical attention I would have made sure they were given it - as quickly as possible. One of the first things I managed to learn as a very new teacher - my first day on the job in the classroom in fact - was how to deal with a major epileptic seizure. I had been told what to do - press the emergency button in the classroom for help - and I did. I also gathered the tiny child up and held him side on so he would not choke. It took every bit of strength I had because even a small child can be amazingly strong when having a major seizure. I am not a big person. I sat on the floor cradling him and hoping none of the children would do anything they should not be doing.
One of the nursing staff was there quickly - a big, strong, male nurse - and took the child off with the words, "Thought he might do that this morning." Great.
I thought of that this morning when I read that some people still won't get their children vaccinated, and still believe that vaccination "causes autism". Because of that some medical staff are said to be "refusing" to treat them. I am not sure what that means. Presumably a child presenting with a wound that needed stitching or a broken arm from falling off the play equipment would get attention. But a child with spots and a fever? 
I could have done what I know some of the other staff did. They would clear the area around the child having the seizure and just leave them to "come out of it on their own". I never managed to do that. The entire time I was in that school I was afraid a child would die on my watch, that I wouldn't have done enough to help. They were my responsibility.
So I wonder about the parents who choose not to vaccinate their children and, if really true, the medical staff who turn the child away. After all, it isn't the child's responsibility to get themselves vaccinated.
I grew up when vaccination for things like rubella were not available. I went through the usual range of childhood illnesses, as did my siblings. We were nursed by our paternal grandmother because my mother and her parents were Christian Scientists who refused to recognise illness. But we did get the available vaccinations. The Senior Cat and his parents insisted on that. 
I just don't understand why people don't give children all the available help.