Their own, or those of others? A difficult question to answer. Most of the usage shibboleths of the modern grammar nazi (aka prescriptivist, peevologist, grammar maven) are not their own, but come from other equally ill-informed pseudo-grammarians. For example, somebody like Dryden comes along and decides
ex cathedra that sentences (which he never really get around to defining) must never end with a preposition. Even the Bishop Lowth found this fiat a bit too much and in his seminal peevological work,
A Short Introduction to English Grammar, (whence many other modern-day usage factoids) he penned:
The Preposition is often separated from the Relative which it governs, and joined to the Verb at the end of the Sentence, or of some member of it: as, “Horace is an author, whom I am delighted with.” “The world is too well bred to shock authors with a truth, which generally their booksellers are the first that inform them of.” This is an Idiom which our language is strongly inclined to; it prevails in common conversation, and suits very well with the familiar style in writing; but the placing of the Preposition before the Relative is more graceful, as well as more perspicuous; and agrees much better with the solemn and elevated Style.
NB, the sentence starting "this is an Idiom" and ending with
to before the semi-colon. Old Bob had a sense of humor that Dryden and his ilk were lacking. But there is hope. Samuel Johnson started out editing his magnificent dictionary as a prescriptivist, but by the end he had pretty much become more of a descriptivist.
