is the legit ones just like... putting carrie fisher in star wars?
usually people bring up anyone who is losing physical control of their voice faculties, so they can have a synthetic voice that matches their natural voice
As an example of this, Sarah Langs uses a synthesized voice due to the progression of her ALS symptoms.
The iPhone has a built in voice cloner hidden in the accessibility settings for exactly this use-case: creating a backup of your voice in case you need it in the future.