Should punctuation in direct speech mirror that of punctuation in the narrative of novels?
Firstly, it needs to be made clear that the kind of punctuation being discussed here applies only to semicolons and colons — in other words advanced punctuation. Secondly, other punctuation (such as the comma, full stop, em dash, and exclamation mark) appear so regularly in novels that it is pointless to argue against the inclusion of these forms of punctuation.
So back to the use of semicolons and colons.
For my part, I do not see why they are entirely necessary, although, on occasions, I understand they do provide another way of communicating an author’s thoughts through their characters. And, when the dialogue is lengthy, varying the punctuation (by using a semicolon for example) may help to communicate the character’s thoughts better.
One reason why I do not think they are necessary in the main is that the comma and full stop do an adequate job of addressing the punctuation of phrases, clauses, and sentences themselves. Another reason is that when I read what a character is saying, I am also putting myself in the place of that character, and I would not speak in such a way that semicolons and colons were necessary — for the most part.
But some authors use advanced punctuation and it appears to work — notwithstanding the point that a comma and a full stop might do the job just as adequately. And here is a final thought that I found on the internet referring to the use of advanced punctuation in dialogue: there is no sense in buying a specialised tool when you can use a general one just as effectively.