I wonder if one of the subconscious reasons for their disdain for philosophy is that these scientists and others are writing books claiming that science pretty much makes belief in God untenable, but they're finding that philosophers who critique their arguments are showing them to be embarrassingly unsophisticated. The animus against philosophy may derive from personal chagrin suffered at the hands of philosopher-critics.
Be that as it may, Hawking and Krauss, for all their brilliance, are astonishingly unaware of the philosophical faux pas that pervades their own writing.
Krauss, for example, made the claim in his book A Universe from Nothing that the universe emerged spontaneously out of a mix of energy and the laws of physics which he calls "nothing." Thus God is not necessary to account for the universe. Of course, this is a semantic sleight-of-hand since if the cosmos was produced by energy and physical laws then there was not "nothing," there was "something," and we're confronted with the mystery of how this energy and these laws came about.
Hawking declared philosophy "dead" in the early pages of his book and then spent a good part of the rest of the book philosophizing about realist and anti-realist views of the universe and the existence of a multiverse.
It's ironic that physicists like Hawking and Krauss would be so willing to deprecate philosophy since their own discipline is infused with it. Every time physicists talk about the multiverse or the nature of time or space or their own naturalistic assumptions about reality, they're doing metaphysics. When they talk about knowledge, cause and effect, the principle of sufficient reason, the principle of uniformity, or the problem of exactly what constitutes the scientific enterprise (the demarcation problem), they're doing philosophy. Whenever they discuss the ethics required of scientists in conducting and reporting their researches they're doing philosophy.
The entire discipline of science presupposes a host of philosophical assumptions like the trustworthiness of our senses and of our reason, the orderliness of the universe, the existence of a world outside our minds, etc. Yet these thinkers seem to be oblivious to the foundational role philosophy plays in their own discipline. Indeed, science would be impossible apart from axiomatic philosophical beliefs such as those listed above.
There's a bit of a joke at Uncommon Descent about this. It goes like this:
Scientist: "Why does philosophy matter?"
Philosopher: "I don't know, why does science matter?"
Scientist: "Well, because scie...."
Philosopher: "Annnnnnnd you are doing philosophy."