It's supposed to be an exchange between the public and artists. The overall purpose is to increase the amount of art available to everyone. Artists get legal protection for a limited time to be able to monetise it. And in exchange the public gets full access to the art after that time is up.
That's not correct. There are other forms of IP besides copyright, such as trademarks, patents, or even trade secrets.
What you are saying is somewhat true for US copyrights (and patents) per the copyright clause in the US Constitution. But mind that typically copyrights are owned by the employer of the creator, who may be a writer, even a programmer, photographer, or any other such professional who may not be considered an "artist".
You would probably not consider yourself an artist for writing comments here, but you get copyright nevertheless.
European copyright has a very different philosophy behind it, which does not consider the public at all. It's quite harmful to the public, actually.