People will do that regardless of incentive. It's essentially a basic brain function, it can't be turned off. I'm discovering a new number right now by posting this comment.

People create cool new numbers all the time without worring about royalties and how-am-i-going-to-make-a-living-from-this-diddly-tune. Copyright is a way to commodify something deeply human to allow capitalists to make money from it. Put it this way, in a post-scarcity money-less world, musicians would still make cool new numbers, advertising people would not be creating any advertising numbers, they would probably make music as well.