Part of the reason is the decline of the semicolon and em-dash. At least anecdotally, I feel that they were far more common in pre-20th century fiction.<p>Consider the opening of Poe's "Descent into the Maelstrom":<p>> <i>“Not long ago,” said he at length, “and I could have guided you on this route as well as the youngest of my sons; but, about three years past, there happened to me an event such as never happened before to mortal man — or at least such as no man ever survived to tell of — and the six hours of deadly terror which I then endured have broken me up body and soul.”</i><p>I think that every modern writer would replace the semicolon with a period. Many of them would also get rid of the dashes and the little digression they contain. So, for e.g.:<p>> <i>“Not long ago,” said he at length, “and I could have guided you on this route as well as the youngest of my sons. Then, about three years past, there happened to me an event such as never happened before to mortal man, and the six hours of deadly terror which I then endured have broken me up body and soul.”</i>