Of course, billions of people also live without any conception of formal mathematics, linguistics, quantum theory, macroeconomics, French, or any other subject usually understood to require study or appropriate cultural conditions. And they could probably continue to live without it even under ideal material conditions. This does not undermine any of those things as useful intellectual tools.
As for whether the understanding of the dialectic is of any use, Loren Graham's study of science in the Soviet Union names scientists who claimed to have been inspired by dialectical materialism, laid out in their work how dialectical materialism was of use to them, did so even when their was little or no pressure to link scientific work to the dialectic, and yet made significant scientific advances. Oparin, Haldane, Kolmogorov and Luria are among the names I remember. And, I'd argue that dialectical materialist thinking has been of use to me in computer and cognitive science.
I've never understood what Marx imagined science to be when he claimed socialism was scientific, but since all the contemporary theories of scientific method that I know of (at least, all the ones that still have any responsible adherents) were 20th century creations, it is a bit ridiculous to expect Marx to have had those ideas in mind. I'd certainly agree that making "scientific socialism" into a slogan is no more useful or meaningful than "socialism makes your whites whiter and your brights brighter."
Physical scientists seem to make do with very little training in method and even less in philosophy. I seem to recall Marx saying something about how the only way we can objectively know anything about the universe is through practice. Looking at science as a form of cultural practice (which most scientists will agree to once you explain what a cultural practice is and let them know that doesn't mean you think scientific theories are arbitrary), I think the dialectical materialist approach is at least compatible with scientific realism and can even be illuminating in understanding it.
Trotsky didn't believe dialectical materialism was the be-all and end-all of method or philosophy, even going so far as to say that the nature of the dialectic was such that it predicted its own replacement. But, he argued that it was the most illuminating method around. That's a very different argument than whether dialectical materialism is a scientific theory.
Materialism as a philosophy seems to be one of the few common parts of scientific practice, but I can't see anyone claiming that materialism is a scientific theory. I'd argue that the dialectic has a comparable ontological status.
Scott Martens