Rheology and thermodynamics are two areas of science that have some unique characteristics. They both are subjects that cut across wide ranges of science, rearing their ugly little heads in physics, chemistry, biology and wide ranges of engineering. This suggests their extreme importance. And yet, despite this importance and wide applicability, it is impossible (as far as I know) to earn a degree explicitly in those subjects. Sure, you can specialize in those areas while doing your doctorate, but have you ever see anyone with a Ph.D. in Thermodynamics, or a Masters in Rheology? Kinda odd, don't you think?
I've tried to come up with similar fields in this situation. The whole realm of "transport phenomenon" and the various subsets (heat, mass and momentum transfer  for those of not trained as chemical engineers) are one, although I'm not as convinced on the subsets by themselves. On the other hand, I've ruled out the idea of the Grand Unification Theory - any of the various attempts to unify the 4 fundamental forces (gravity, electromagnetism, strong nuclear force and weak nuclear force) as being just a part of physics  and not really applicable to chemistry, biology... Ditto for the String Hypothesis .
Scholarly journals present a mixed view of this matter. There are several journals devoted to just rheology (Journal of Rheology, Rheologica Acta,...) along with many scholarly societies devoted to rheology but thermodynamics isn't quite as well represented and I am not aware of any thermodynamics societies. And transport phenomena (as a whole) is totally without any journals or professional organizations, while the subsets are well represented.
As for the industrial world, I don't ever recall seeing job opening where these specializations are the leading or major component of the job description. Certainly you can see "rheology" far down the list for some positions, but have you ever see a job for a thermodynamicist? Even the people that are rheologist tend to carry that around as a sub-description as they usually have primary interests in a chemical/physical situation that gives rise to the rheology of interest.
So what does this all mean? What is the impact on us? All of us carry mental constructs around in our heads which we use to divide the world up and thereby give us a perspective on how we see things. Would the world be better off if you could major in thermodynamics? If we did have thermodynamicists?
 momentum transfer = fluid mechanics
 To anyone wanting to argue that chemistry and biology are both just applied physics, I've dealt with that reductio ad absurdum before.
 How can anyone call it String "Theory" when it hasn't been put it up to any experimentation yet?