This article is from the comp.sys.acorn FAQ, by Paul Vigay with numerous contributions by others.
Simply because of the wide distribution that the FAQ has. Every time the FAQ gets posted it gets automatically archived into various FAQ databases, propagates on ancillary networks only loosely connected to the net (BBSes in particular) and reaches a wide variety of people whose skills at navigating the net vary considerably. Occasionally it gets copied onto CD ROMs, Magazine discs and extracts get used in various publications from time to time.
All this just from the posted copy of the FAQ.
Given this wide reaching nature and the general idea of an FAQ being to reduce network traffic by providing the answers to common questions immediately then I see clear justification for continuing to post the full FAQ.