There’s legitimately no reason to cast famous live action actors over actual voice actors in animated media
Voice acting is a completely different discipline than stage acting and screen acting. There’s some overlap, but they’re not interchangeable. Just because someone is a talented screen actor doesn’t mean they’ll be automatically a good voice actor. A lot of extremely talented live action actors also happen to be dogshit voice actors. Part of this comes from hiring what are essentially rookies and expecting them to perform to snuff but part of it is live action actors consistently not taking voice acting roles seriously and undervaluing the medium. They either phone it in or treat it like a joke. You don’t need to be voice director to know it’ll be a struggle to get decent performances out of people who think voice over work for animated media is kiddie shit and an easy paycheck.
You also don’t get most of the fame value that live action actors bring to the table. A large chunk of a screen actor’s brand is their appearance and recognizable face. The vast majority of the audience recognize actors by faces, not by names. Most screen actors don’t have distinct enough voices to be instantly recognizable. What’s the point of sacrificing a massive amount of budget to shell out for a famous actor when 90% of the audience won’t recognize or care that it’s their voice they’re hearing coming out of the characters’ mouth? You might as well burn that money.