With rare (but large enough to be notable) exception, they already are.

As a musician, few things anger me more than when a politician claims to be clamping down on speech to defend my "property."

That's admirable, but I'm not sure your viewpoint is so widespread. At least among authors, many view their work as property and would be outraged if anyone tried to "take it away from them".

I think most people now (artists or not) view one's copyrights as real property, and their eventual expiration as an antiquated idea.