Dear Luther,
I've been puzzling over your observation for nearly 15 years, and I also fail to understand why Mathematica/Wolfram Language gets dismissed by my colleagues so haphazardly. In discussions with my colleagues about this question, I tend to go in listening mode and don't advocate on one side or another. I'll try to summarize what they say below.
Some background:
I'm a professor at MIT in physical sciences and engineering. I've been teaching a course on mathematics and problem solving in materials science for about twelve years, and I use Mathematica extensively in my course. I can't judge the efficacy of my course objectively, but my students generally have very positive evaluations; I've been given MIT's highest institutional teaching awards, as well as the School of Engineering's. I believe that these awards reflect the quality of the Mathematica based course. I give nearly all of my research presentations using Mathematica and these are received well (however, such feedback tends to be biased towards positive)
The summary (I don't agree with many of these, and am still honing my counter arguments)
1) Mathematica is not as fast as X (X may or may not be a compiled language).
2) Mathematica's syntax creates too steep of a learning curve.
3) Our (particular) scientific community uses X; so there are many more routines and working examples in X
4) I am already using X, why should I change?
I believe most of the above are the result of "user inertia".
I don't hear the comment that Mathematica gives "bad results" so much now. I doubt if many faculty roll their own algorithms, but are probably thinking back to when they were postdocs or graduate students--however, there are happy exceptions to this
I believe that the best way forward is to offer students a choice; and hope that they will make an unfettered choice of a their preferred programming language. However, I am not so optimistic: a student who went to graduate school at a university down the street wrote to me saying, "I'm taking this class and they insist on using X and I asked if I could use Mathematica instead, and he said no. We were doing more advanced things in 3.016 ( the sophomore class I teach)."