Dogs also love to wrestle over the stick/ball/... Think 2 dogs holding onto the same stick with their teeth while growling and pulling as hard as they can, they're having fun.

The dog I grew up with (malamute) would fetch something once and then have you try to get it out of her mouth, which was impossible to win for a human, so you'd have to feign giving up and then she'd drop it. And if you then threw away the object again, she would give you "the look" after which she would saunter off and ignore you. So I'm pretty certain that she didn't like fetching, but she loved wrestling and pulling.