The realizations of the remake in the Harry Potter film had some mishaps to some of the actors. No offense, but using an actor that has a complete skin tone as the character erases the whole culture of said character, such as Snape. 

Think of this: If this was set in live action, actors are most likely going to engage in some harmful and uncomfortable actions based on what's assigned for them to do in the filming(such as pretend sex or kissing or arguments). WHEREAS, if it was hand drawn digitally, actors can only rehearse a few times for their script without multiple cuts as it is read on the script. Plus, for the characters, they could look like the people from the book when hand drawn to the author's liking. Furthermore, live action actors wouldn't have to do makeup to fit the character's looks.