...which is a word defined first by his friend and fierce defender, Huxley.
I do not think that Darwin, Huxley, Einstein, or Hawking are ambivalent about their lack of belief. What I think is that the description of atheist has become so culturally toxic that it has become almost an insult.
Darwin and Huxley would never had called themselves atheists in Victorian England any more than Einstein would have done the same in the USA during his life. Hawking is an outlier. I think he is basically channeling Einstein and his beliefs.
The reason that I explicitly label myself as an atheist, and that I eschew other labels, is that I do believe that evidence shows that there are very likely not any gods. The most accurate expression of this is to call oneself an atheist.
I cannot prove there are no gods. But it seems to me that the burden of proof is on the theists. They are the ones making claims of an entity whose attributes of which they cannot even agree. William of Okham would slice such claims right off.
But, no. I cannot prove there are not gods. But the null hypothesis must be that there are not unless there is evidence to the contrary. I see no such evidence. The universe seems pitifully ignorant of any such hypotheses.