How many people would publish if no option to have a copyright existed at all?
Well, all the people who published works before 1710 had no copyrights. All the people who published after that, but not in England had no copyrights until various countries slowly adopted copyright (the US picked it up in 1790, the French after that, and most of Europe in the 19th century -- and they only exported it to the rest of the world by means of colonialism, not on its own actual merits).
Plus there were various limits, e.g. the US only granted copyrights to Americans until almost the end of the 19th century; British authors had no option to get an American copyright at all... unless they became American citizens.
More recently, various classes of work were ineligible. For example, architectural works (in practice, buildings) were uncopyrightable in the US until 1990. Were no buildings designed and built in this country until architects were given copyrights?
What I think you're missing here is that there are a plethora of incentives for an author to create and publish a work. Money gained by exploiting a copyright on the work is but one of those incentives, and often is not the most important one, and also often is not an essential one.
I certainly agree that it can be useful, but that doesn't mean that we ought to go hog wild with it; as with many other things, a little might be beneficial, but too much can be harmful.
And what is the point of having a copyright in the first place if the creator isn't supposed to be permitted to try and exercise control over who may copy their works?
The point is to grant authors copyrights as an additional incentive in order to entice them into creating and publishing works which they would not have created and published, but for copyright. If they would've done it anyway, the copyright is superfluous, and granting it would be wasteful. If they require more copyright than is healthy for society, all things considered, we're literally better off not granting it even though it means we'll be bereft of the work in question.
It's not intended to give authors control over works for their own sake. That's just the means by which it functions. It's intended to produce a public benefit. And while the public does benefit from having works created and published, it also benefits from not having anyone controlling works.