Historicists meet the canon
In the introduction to The Antichrist's Lewd Hat (Yale, 2002), Peter Lake writes:
In this respect the book has much in common with recent trends in literary-critical and literary-historical writing on the period, which have sought at the very least to problematise the canon, setting 'great books', the old staples of literary study, into increasingly uncanonical, quirkily 'historical' contexts, juxtaposing one sort of literary text with another, the high with the low, what used to pass for 'the literary' with what used to pass for 'the historical'...[description of new terms for this practice follows]...Now everything is conceived of as text or discourse, to be read and glossed against one another in a virtually infinite series of combinations. Ironically, despite this all-out assault on both the notion of the canon and the relationship between historical context and literary text, nearly all such exercises, when conducted by literary scholars (by which I mean in this context people employed in English departments), end up discussing the most canonical of canonical texts. (xxx-xxxi)
Actually, a different "irony" is at work: the practical failure of the "all-out assault" on the much-maligned canon. As Morris Dickstein notes, "the theory era is effectively ending and the public intellectual tradition is reasserting itself, along with a renewed attention in the aesthetic that many theorists dismissed as no more than an ideological formation." But the new historicism, like deconstruction, needs complex literary texts in order to work its magic; any critical theory grounded in close reading will, of necessity, focus most intensely on works that respond to such an approach. George Eliot, yes; G. W. M. Reynolds, perhaps not so much. Moreover, we tend to reward the critical virtuosity (for lack of a better term) required to link the most aesthetically powerful texts to their historical contexts; there's no such effort involved when it comes to an obviously "engaged" writer. All those who want to analyze the circulation of power in the poetry of Ernest Jones, raise your hands.
There's something else at work: the economics of hiring and publishing. Very few dissertation directors will allow a student to write a thesis on entirely non-canonical authors, for the very pragmatic reason that hiring committees are almost always composed of people outside the desired field. (Last year, for example, saw yours truly on the medieval search committee. Does this strike you as a medievalist's blog? No? Didn't think so.) It's very likely that everyone will have read Geoffrey Chaucer, and reasonably likely that everyone will have heard of John Gower, but not so likely that everyone will be familiar with Hrotsvit of Gandersheim. For that reason, most directors will stipulate that somewhere, sometime, somehow, the student must write at least one chapter on a widely recognizable author. What looks like a mere accident--the impossibility, in most departments, of assembling a hiring committee composed solely of specialists in a given field--thus builds a certain "conservatism" into the discipline, no matter what lip-service it pays to dismantling, disrupting, displacing, or otherwise dissing the canon. Similarly, it is, in fact, extremely difficult to sell a book manuscript about only non-canonical or non-literary figures (although, obviously, it can be done; from looking at sales catalogues, it's my impression that some of the commercial academic publishers, like Palgrave Macmillan and Ashgate, are more willing to consider such books than are the university presses). My own book, for example, sprouted a chapter on George Eliot because the reader and publisher were concerned about the lack of major female authors. Not any female author would do; what the book needed was an established, "name" figure.