That's correct, a actor can get sick while a 3D model doesn't. And yes, actors can refuse sex and they have all the rights to do that and we shouldn't judge them for it. But in my opinion, not every novel doesn't need to have a straight up hardcore sex scene. Sometimes it's also nice to play a "softcore porn" game that doesn't heavily aimed at penetration and sex scene's, but rather just nudity and or other type's of porn genre's and you can perfectly use real actors without having the fear that they might refuse a sex scene.
And besides, you always need to tell your idea's, story and what kind of role they get, before hiring. So, they know what to expect.
