What kind of readers you have in mind when you write in an encyclopaedia something like this: The Abyssinians are ‘black, or almost black, but not as ugly as the negroes.’
Probably, when Encyclopaedia Britannica editor William Smellie wrote (or copied) this in 1768, he did not imagine that black people read it. 
Dennis de Coetlogon, nearly a contemporary, seems not to have been very fond of craftsmen, servants and the lower classes. In the articles he complains about them. He preferred to write for gentlemen, and so his Universal history ‘features a strong stream of elitism’, with articles about falconry and other subjects for princes, Loveland explains. Among the subscribers were actually some craftsmen, but they must have been extraordinary rich to afford such an expensive work. 
Considering the immense costs, the readers of encyclopedias have been a very small group for a long time. According to Luff, the prefaces of medieval encyclopedias usually did not limit themselves to a certain readership. But even the more than 380 manuscripts of the Elucidarium came ‘practically never came into the possession of laymen’. The Livre de Sidrac, again, was read only by noblemen. An extreme example is the Hortus Deliciarum: Abbess Herrad compiled it exclusively for the nuns in her abbey. There it stayed for three and a half centuries. 
In the high time of encyclopedias, the 19th and 20th centuries, publishers liked to flatter their buyers and stressed out how smart a person must be who uses an encyclopedia. And when someone complained that encyclopedias provide only superficial knowledge and don’t really educate the readers, the answer of the publishers was: Our readers are educated already.
As Harvey Einbinder noticed, the Encyclopedia Americana of the 1960s boasted its ‘accuracy, thoroughness, and ease of use make it equally indispensable to the junior high school student and the most advanced scholar.’ He doubts that a text can really be indispensable for both, but ‘such difficulties are ignored by the copywriters and executives responsible for such exaggerated statements’. 
And Wikipedia? Some people believe that a new medium is a chance for a new culture, that now the time has come to give every single person on the planet access to the sum of all human knowledge. Indeed, they get the access, but as always the smart will be become smarter and the others… don’t, or worse.
Ulrike Spree at the end of her thesis says that the best reference works are those which listen to the motto of the publisher of Junior Pears Encyclopaedia: ‘A book like this one ought to be shaped not only by a body of contributors but by a body of readers.’“ 
She might give Wikipedia a chance, I hope.
 Frank A. Kafker, Jeff Loveland: William Smellie’s edition: a modest start. In: Frank A. Kafker, Jeff Loveland (ed.): The Early Britannica (1768/1803). Voltaire Foundation, Oxford 2009, pp. 11-68, here p. 29.
 Jeff Loveland: An Alternative encyclopedia? Dennis de Coetlogon’s Universal history of arts and sciences (1745). Voltaire Foundation, Oxford 2010, pp. 74-76.
 Robert Luff: Wissensvermittlung im europäischen Mittelalter. ‘Imago mundi’-Werke und ihre Prologe. Max Niemeyer Verlag, Tübingen 1999, pp. 423/424.
 Harvey Einbinder: The Myth of the Britannica. MacGibbon & Kee, London 1964 (reprint 1972), pp. 321/322.
 Ulrike Spree: Das Streben nach Wissen. Eine vergleichende Gattungsgeschichte der populären Enzyklopädie in Deutschland und Großbritannien im 19. Jahrhundert, Niemeyer 2000, p. 328.