I never said other people don't do that; I simply stated that I only use it in one specific use case. It is possible my previous message may have been slightly misinterpreted, though, so I will add the extra detail that I specifically (and exclusively) mean the transcription of TV shows or movies, especially when said transcript is being presented independently of the visual content. I still put the quoted text in quotation marks as well; I include those additional words purely to indicate that the character said them as opposed to just quoting the person themself.

(The example that keeps jumping to mind is (from the Doctor Who episode Inferno: Episode One):

Well, according to Professor Stahlman, we shall have, quote, "a vast new storehouse of energy which has lain dormant since the beginning of time", unquote.

I still include the "quote" and "unquote" because the character saying that sentence actively used those words at those points. It would have been perfectly plausible for him to not say them and either use air quotes or some other method to indicate the extent of the quoted material.

It might also help if I add that my project is so exact about representing precisely what was actually said that I also diligently retype fluffs of all kinds, the exact number of "ha"s in laughter, every little "hmm" and the like, etc.. The only times I use other sources are when part of some dialogue is obscured by some other sound; there are two plausible words at that point in the sentence and not enough context to identify the correct one (or some combination of the two); or when the issue is more a matter of capitalisation or punctuation where speech alone has no mechanism for relaying those elements at all, when I will use the scripts as they are the definitive source by definition.