Answer

I can think of several explanations: 1. Specifically on the issue of authority, it certainly would not be advisable for the Haredim to deal with it, because otherwise Haredism would disappear from the world. 2. Traditionally, it was not customary to engage in methodology and reflection on the system. This is a modern phenomenon (scholarship), and as such it appears less in conservative societies. When I wrote my first article on an a fortiori inference (Bedei Bad 2), I went down to the Bar-Ilan library to look for material on it. I saw a shelf on the hermeneutical principles by which the Torah is interpreted, and every last one of them was by Religious Zionists.
Recently the situation has changed a bit (there is more of a tendency to engage in scholarship even in Haredi society), because modernity is penetrating Haredi society as well—just at a slower pace, of course.