A few reasons:
Most of modern economics consists not of value-free research, but of shilling for the state.
Institutional factors in economics departments.
Many “Austrians” who present themselves in public as such are not economists and don’t explain Austrian economics.
A sense that the only Austrians people hear about are doom-and-gloomers. People don’t like bad news.
A fear of anti-semitism - they associate Austrian with Paul with anti-Fed with militias.
It just plain doesn’t look scientific.
Perhaps most importantly, it requires a fundamental shift in understanding as to what economics is - and if you want to get policy out of it, also as regard what society is.
What we can do about it -
Get real Austrian economists out into public more to explain our ideas.
Start pursuing Austrianism through other means if the economics profession isn’t receptive. I, for instance, am a grad student in math, planning on studying connections between Hayek and chaos theory.
Be unafraid to present premises, not soundbites. We simply must focus on subjectivism. (A study of past revolutions, by the way, suggests a pattern - first, the revolutionary ideas must be current among the intelligentsia, then events set off the mob. Appealing to the public first doesn’t seem to work for truly revolutionary ideas, only for minor changes. The French Revolution suggests to me that people looking to make fundamental changes in society had better be careful about why their friends are. So, forming temporary alliances with dangerous figures on the right could be, well, dangerous if we are ever successful.) So, there’s no need to avoid dorkdom - we need to appeal to the intellectuals. We already have popularizers - Paul and Schiff come to mind. Professionals need to turn inward and get friends in the academy. Not just economists, but in all subjects, particularly philosophy and politics, but also psychology, math, and so forth. As Israel Kirzner taught last week at FEE, Menger had a flash of insight - similar to seeing clearly, for a short time, when lightning strikes. That flash of insight was that, within the parameter of physical reality (there is no economy on the surface of the sun), everything that we see depends exclusively on the subjective preferences of the consumers. Consumer demands even determine, again, in the context of reality, what raw materials are available - availability depending on such things as the existence of machines to access it. When we say “much of Austrian thought has been absorbed into the mainstream” this is what we mean to leave out - but it is what is absolutely crucial to Austrian thought. The ABCT could be written in neoclassical, formal analysis terms, or in Marshallian terms, even though it wouldn’t be. What is unique about us, what is true about us, is subjectivism. Not just the subjective theory of value (Kirzner sees BB’s acceptance of subjective theory of value without understanding the all-embracing nature of subjectivism as the cause of BB’s mistakes in capital theory) but the subjective theory of everything.