Why is ‘such an one’ obsolete?

From Inventing English: A Portable History of the Language by Seth Lerer (2015)...

Other features of Shakespearean pronunciation include the pronunciation of the word one. Descending from the Old English word an, “one” was the stressed form of what would become, in unstressed positions, the indefinite article a. Our modern pronunciation with the initial glide [wun] did not appear until the eighteenth century.

A related issue discussed on wordinfo.com...

Occasionally in modern writing and speech and regularly in the King James Version of the Bible, an is used before "h" in a stressed syllable, as in an hundred.