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. Why should people be so preoccupied with hobbies? Hobbies have their place but it seems silly to dedicate ones life on something as trivial as a hobby.
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
Since humans already survive, they do not. Just like humans already can move from point A to point B without cars or planes, humans survive without artificial hearts. So those things are hobbies in the same way cars and planes are toys.
Any human will die at some point without artificial hearts, meaning all humans are slowly dying due to non availibility of artificial hearts, further meaning that all humans are slowly failing to survive without artificial hearts.