You are absolutely right, Charles. However, you mistakenly assume that these luminaries want to produce social change rather than to sell their intellectual commodity. Once you change that assumption, pomo and other modes of intellectual commodity production will appear in a very different light.
You see, one cannot sell commodity to which one does not have exclusive ownership rights which can be effectively protected. In economics, such commodities are called "non-excludable" goods (i.e. non-payers cannot be excluded from enjoying the good in questions) and are believed to be under-produced in the market because producers have problems receiving payments from all who use them. This is why such goods are also called "public" or "collective," believed not sell very well on the market because of the "free-rider" problem i.e. users who do not pay because they cannot be easily excluded from enjoying the utility of the good in question.
Many cultural products, especially theories, are public or collective goods by nature. Once someone invents a theory, nothing prevents everyone else from "appropriating" it by mere intellectual comprehension without paying a penny to the original producer. This is why those producers who want to maximize the sale of the intellectual commodity they produce, they must use some artifice that prevent the "free riding" public to easily appropriate their products.
Obscurity is perhaps the oldest trick on the book to accomplish that. Of you explain the relationship between A, B and C in simple terms, that explanation, once understood, can be repeated and spread to "the masses" as you initially suggested, but the producer will not receive a penny or even recognition, because his/her invention will soon become common knowledge. If, otoh, he/she wraps that explanation in the layers of obscure and incomprehensible verbiage - the spread of that intellectual product will be difficult, if at all possible, without people buying the whole package in the form of a book or other recording - which suits the interests of the producers of the intellectual commodity in question.
Another force working in the same direction is market demand. The lit-crit audiences are not content with the simplicity of the everyday literature, just as they are above dining at fast food joints. They demand something more complex, more sophisticated, more exotic and above the ordinary tastes. Therefore, they are unlikely to buy a fast-food-for-thought book with simplistic language and explanation. However, these are the folks who buy the books, as "the masses" settle for lighter forms of cultural productions, such as tee-vee, or moooovies. The producers know that and tailor their intellectual commodity accordingly.
In sum, you have two forces - the supply of intellectual commodity via markets (rather than alternative venues), and the demand for sophisticated and exotic intellectual experiences that drive the obscurity factor in the intellectual commodity production through the roof. And it will remain so as long as culture and intellectual inquiry are a commodity rather than pursuits of every human being. Did not the Old Man write something about fishing in the morning and writing poetry in the evening?
Wojtek