I wouldn't say that people don't care because they know there's only one official version of it hanging somewhere. I think it's more so that people don't know

I wouldn't say that people don't care because they know there's only one official version of it hanging somewhere. I think it's more so that people don't know that they're looking at a fake. I would be surprised if you told someone that the painting they're looking at is fake and they're response is "oh I don't care". I'm sure they'd be at least a bit disappointed.