Mostly due to my neurologists not being able to determine the cause of the neuropathy in my feet. I'd be referred to another one, and they always wanted to perform the test themselves instead of looking at the results from the previous test.
My last neurologist did this test, along with some blood tests, and a skin punch biopsy on my lower legs, and everything was "normal", hence the diagnosis of idiopathic poly neuropathy. It took him over 2 years to come to this conclusion.
After that, he basically said he couldn't do anything else for me. He has since retired.