A font designer doesn't do more work when their font faces get used in different works. Stock photo creators don't do extra work when their images get used in new media. Musicians don't do extra work to have their songs used in commercials and movies.

Virtually anyone can use their own voice (or an entirely artificial one) in some work. If folks are willing to pay money to use one particular person's voice, what's the harm in that? If they don't want to pay to use that voice, they have literally billions of other options.