> Well, I just decided that building an artificial heart or defeating Parkinson or Alzheimer's, curing diabetes, solving cancer are under the umbrella of hobbies

They fall under the umbrella of survival, because as things stands today , you know that one of those things will eventually be the thing which gets you . Very much like Feynman and Von Neumann knew too, but decided to dedicate the practical part of their theoretical skills to building a toy such as the atomic bomb