Rules have locked into our collective thinking about what serves as ‘elegant writing’. As deemed by John Dryden, it is inelegant to end a sentence with a preposition. He was, at first mention of his observation, criticizing another writer.
It seems the best reason not to end a sentence with a preposition is the powerful weight of the last word. Endings are ‘the weightiest’. Do you really want ‘of, on, with, for, etc’ as your triumphant finale?
Full historical account of the codification of this grammatical rule here.
Unity in Writing 