Philosophy of science is about as useful to scientists as ornithology is to birds.
This is a clever way of saying that a scientist doesn't need to think about what he's doing, any more than a blue jay needs to study the Blue Jay Way. And this is quite true, as long as the scientist isn't looking to break new ground in science, but is content to work on the usual problems in the usual ways. C. S. Peirce explains:
The theory of any act in no wise aids the doing of it, so long as what is to be done is of a narrow description, so that it can be governed by the unconscious part of our organism. For such purposes, rules of thumb or no rules at all are the best. You cannot play billiards by analytical mechanics nor keep shop by political economy. But when new paths have to be struck out, a spinal cord is not enough; a brain is needed, and that brain an organ of mind, and that mind perfected by a liberal education. And a liberal education—so far as its relation to the understanding goes—means logic. That is indispensable to it, and no other one thing is.
Logic here ‘is the art of devising methods of research,—the method of methods’; it is also a ‘normative science’, a method of evaluating methods. Peirce made these remarks in 1882, introducing the course in logic which he taught at Johns Hopkins University. If he seems to use the word more broadly than we typically use it today, perhaps it's a sign that we have still not taken the path of ‘liberal education’ to which he pointed so long ago.
Peirce also identified logic with semiotic(s), the study of how signs of all kinds operate. My gnoxic inquiry likewise delves into the roots of significance. I am always asking, How do you mean?. Now, you don't need to answer that question—in other words, you don't need a theory of meaning—in order to commit an act of meaning. You do it all the time, without knowing how. But what if you're aiming to boldly mean what no one has meant before? Then you might need to think about how you can do it. And that's what intimologies are all about.
It's true that a specialist (like Feynman) doesn't need philosophy of science, any more than a bird brain needs philosophy. But the most illuminating discoveries tend to be made by those who cross the old specialist boundaries. I will leave the last word on this to Peirce, continuing from the quote above:
I do not need to be told that science consists of specialties. I know all that, for I belong to the guild of science, have learned one of its trades and am saturated with its current notions. But in my judgment there are scientific men, all whose training has only served to belittle them, and I do not see that a mere scientific specialist stands intellectually much higher than an artisan. I am quite sure that a young man who spends his time exclusively in the laboratory of physics or chemistry or biology, is in danger of profiting but little more from his work than if he were an apprentice in a machine shop.The scientific specialists—pendulum swingers and the like—are doing a great and useful work; each one very little, but altogether something vast. But the higher places in science in the coming years are for those who succeed in adapting the methods of one science to the investigation of another.…
Now although a man needs not the theory of a method in order to apply it as it has been applied already, yet in order to adapt to his own science the method of another with which he is less familiar, and to properly modify it so as to suit it to its new use, an acquaintance with the principles upon which it depends will be of the greatest benefit. For that sort of work a man needs to be more than a mere specialist; he needs such a general training of his mind, and such knowledge as shall show him how to make his powers most effective in a new direction. That knowledge is logic.
— Peirce (EP1, 212-13)
(By the way, Peirce himself was a ‘pendulum swinger’ in the employ of the U.S. Coast and Geodetic Survey, and made specialist contributions to several fields; but his first and lasting love was logic and philosophy.)
