Its an art actually or a profession. A lexicographer is someone who writes a dictionary.
To put simply, lexicography is the art of writing dictionaries. Its divide into compilation and research on history etc of words in any language.Wikipedia articleSimple definition
way to make money! No, seriously
, words are sort of 'standardized' through the use of a dictionary. Without a single standard, there will be too many different spellings and this will only make things difficult. Consistency of language is very important not to mention in legal documents.
Without a formal study and compilation of words, a language may very easily become corrupt obsolete (as users will migrate to a more standard language eventually).
Before there were any dictionaries, writers like Shakespeare often mis-spelled but then these words become commonplace and eventually added to a dictionary. Lets suppose there were still no dictionaries, then some new writer would mis-spell and this will surely confuse the readers. Please search for proof before you incorporate any of this in an essay.