I can understand it to a point, mainly as an artist and writer. Personally, I'd have no issue with people using my works as inspiration or creating fan works/parodies/satire associated with either or using similar to almost identical character/creatures etc in my original works. The issue comes up though is association. Theres things I don't want to have my work associated with (namely politics/current issues) so copyright would allow me to limit those who might use it in such associations (if they're being jerks on purpose about it, purposefully going against my wishes).

Same with how disney is super on target with their copyright because they don't want anything not "family friendly" associated with their brand while they retain control. They do take thing rather far though to the "no one can" side which I disagree with- especially when (as it's happened before) they essentially use smaller creators as product testers then hit with a copyright claim and turn around to sell near identical products they had removed.

As for specific copyright of an image/book, if I make it and am selling it myself, I'd definitely copyright it becuase (while not the intention when making it) its a way to support myself and future creations. As much and common as people say "it's for passion/fun you should do it for free/give it away for free" the time and supplies ain't that so it's gotta be funded somehow. In that instance I wouldn't be ok with someone taking it and sharing it where I haven't myself done so- be it for attention (karma farming and such, considering its rare for people to back track to the original creator from posts if theres credit given) or "easy money" such as uploading on Chinese sites and losting for cheap to send out as many as possible (as often happens with popular artworks).

If I'm not selling it, I do agree that a copyright doesn't really make sense and is over the top to do. (Unless of course there's a legitimate fear some else would file a false copyright license and try to outright steal legal rights from me/the original creator- seen some horror stories of people with horrible exes who try this with work they made while with them)

All that said, I majorly create for myself and share so I often am not putting myself in a position for need to copyright. (I do have works I'm doing specifically to sell so those would be a bit more "this is mine, you can have if you pay", but as of the current everything has been for passion and thus I'm on the "feel free to use" side.)