I don't think ANY doctor likes to tell a patient that they have a disease or disorder that is not "fixable". And MS is one of those diseases that isn't "fixable". It's not like, "...take two of these pills every day for a week and you'll be cured". It's, "...inject this drug, deal with uncomfortable side effects, and maybe you won't be as bad off as you would have been had you not injected the drug."
Or, when I was diagnosed, 25 years ago, and found a musty old medical books that described MS as a "disorder of the central nervous system leading to severe disability and eventually death...."
So doctors prolong telling a patient as long as possible, until they are SURE they know what they're dealing with. It's better these days, when there are drugs and treatments available, but still tough, when it can't be cured.
...I am not a doctor, nor health professional, and don't pretend to be one, here.....