While I don't question that statistic, it doesn't make much sense to bring it up to me: I find it irrelevant. Here's why: it doesn't really matter that 19 medical conditions out of 20 cannot be cured. Do these affect your quality of life the same way tinnitus does?
The common cold cannot be cured indeed. It's probably included in the statistic. But it's largely irrelevant. Diabetes also doesn't have a cure, but for many an insulin injection will let you carry on with life without much trouble or pain.
It's the fact that tinnitus can have such a devastating effect on quality of life possibly until death that makes it important to focus on. If you want to draw analogies to diseases that don't have cures, do it to Alzheimer's for example, or Huntington's, or some types of cancer.
Lumping it with "all incurable diseases" dilutes the importance and urgency to either find a cure or ways to manage it in such a way that we can regain some quality of life. Forget about fixing the common cold: focus on tinnitus instead (yes I realize that you can have severe complications from the common cold, but you get the point).
Finally, I also find it counter productive to "look at famous people with tinnitus", as if "they went on to do great things" was the ultimate goal in tinnitus sufferers' life. I'd be content with not being famous and not have tinnitus. I don't care for fame: being without tinnitus is much more important to me. I suspect for many others here too.
Yes Beethoven did great things, but he was suffering immensely because of his condition, and I don't imagine anyone would want to "follow his footsteps": his condition sucked, whether he was famous or not, whether he did great things or not.
Health is more important than fame.