Because the tool can generate output faster than human employees alone can (and they control the "legitimate" gate by which other people can use those characters in the tool).
The consequence being that for everyone complaining that AI is disrupting artists right now: these will, in hindsight, be the halcyon years. Even if we assume the copyright arguments hold water in court and AIs trained on other people's copyrighted material are ruled poison-fruit machines, the end result isn't the end of synthesizing-AIs... It's synthesizing-AIs only being owned by people with a big enough data portfolio to train them. Techno-anarchy replaced with techno-corporatocracy, and the smaller-volume artists still lose on being unable to out-produce their competition in an art market.