You obviously don't know any artists and aren't one yourself.
Many if not most of the artists I know, have met, or worked with [both inside and outside of academia] do what they love in such a way that what you're talking about [pay them by the hour] is not even remotely feasible.
Among other things:
* They tend to work for enormous lengths of time on only one thing. Writing a book, for instance, can take years - and often if not usually requires such a devotion of time that doing anything else - like making money by some "normal" means so they can just plain survive, let alone afford to work on their creation - is next to impossible.
* They never get paid -at all- for 80-90% of their "work" [yes, I'm making up numbers, but based on personal experience and observation and interaction with MANY artists this doesn't seem like an exaggeration]
* Most of the artists I have met and known -never- recover anything like what their time "should" be worth for their works of art, even if they do get paid for them. Many works of art -never- make money enough for the artists to even cover total materiel costs let alone how much time it took to create them.
Funny thing is that I'm usually on the side of the argument that you are - I think that copyright as currently implemented in most countries is ludicrous. I also think that the idea of perpetual royalties is outright stupid, and that copyright terms should be shorter than they are.
I can't agree at all with the idea that artists try to somehow get paid hourly for what they do, though. There are too many reasons that idea is utterly impracticable.