Random TikTokers will use AI that sounds like a celebrity, and they get away with it. There are many reasons why it's not a big fuss. They're not really selling a product directly, so it could be considered a fair use, unlike ChatGPT which is a paid product (they're literally selling the voice as a feature). There is also the intent; a Morgan Freeman AI voice on a random TikTok video is obvious to a reasonable person to not actually be his real voice, so you can't really make any sort of claim that they're masquerading him as actually saying whatever the script is. It's just for fun. And finally you can't really sue thousands and thousands of TikTokers.