You might remember an older xkcd comic ranking various sceinces in terms of their purity. Psychology is just applied biology, biology is just applied, chemistry, chemistry is just applied physics… etc. Math is at the top. (Philosophers would like to think they’re the top level, one rank above mathematicians.)
It’s all in good fun, and it happens within disciplines as well. There’s occasional good-natured sniping between experimental and theoretical physicists, and between the various sub-disciplines at different energy scales like particle physics and solid-state physics.
The story more or less is that knowledge gets generated at one level and passed down to the next for further processing. The mathematicians generate Mathematical Truth, the physicists use it to develop the Laws of Nature, the engineers use those laws to create Useful Devices, and so forth. But though that’s the story, it’s not quite true. Knowledge flows in all directions. Physics has guided pure math on numerous occasions (just look at Hilbert…or Newton and Gauss for that matter), while engineering and physics are often almost indistinguishable. The large-scale projects in fundamental physics involve collider design that’s simply an epic engineering problem, and many times in other fields the most interesting problems in physics and the most interesting problems in engineering are the same thing. There’s high-temperature superconductivity, nanotechnology, the intersection of solid-state and materials engineering, pretty much everything involving lasers, and so on.
Which is all to say that the rivalry between disciplines is not so far removed in spirit from the rivalry between the branches of the armed services: at the end of the day we had all better be on the same team.
(Though I have to admit it won’t stop me from the occasional engineer joke anyway.)