You are, I assume, aware that the days of the Alexandria library copying all works that entered the city were well over a thousand years before the printing press was even developed, let alone copyright created.
You were the one who claimed that most would-be pirates were discouraged from doing it prior to the invention of the printing press. Guess what? The high cost of making copies (and the relative lack of literate people to share them with, assuming that the author himself was even literate) discouraged authors from writing things down too.
Also, creators who did not want their works copied could prevent Alexandria from copying them by simply not going into the city
Wrong. You're conflating authors with their works. The only sure way an author could prevent Alexandrians from copying their works was to not create works in the first place.
If they created works, even if they were not written down, nothing stopped someone else from writing it down. (For example, Socrates never wrote anything; what we know of him comes primarily from the writings of his student, Plato; Another example is from the days of Elizabethan theater, when printers would have people dictate the scripts to plays, sometimes actors who had memorized the lines, sometimes just people with good memories who had been in the audience)
If works were created, written down, and shared with anyone, there was absolutely nothing that could keep the scrolls from getting copied or moved. Consider Virgil, who wrote fanfic (The Aneid) based on the epic poems of Homer (The Illiad and The Odyssey), but wanted all the copies burned; this was ignored, and the world is better off for it.
Fundamentally, it's the same issue with secrets, or any other information. The only way to control the spread of it is to either convince other people to respect your wishes (which they may or may not do according to their own self interest, and other factors), or to never tell anyone.
I don't think we can credit copyright with the increase in the number of works in existence in recent history, as compared with ages past. The real credit is probably owed to increases in literacy, improved artificial lighting, the development of printing (as well as improved paper and ink to support it), greater leisure time available due to a variety of technological and social advances, increases in the internal stability of much of the world (hard to sell books when bandits rob every wagon, or war ravages the country), etc. Copyright can be nice, but it gets way more credit than it deserves.
Copyright (by which I mean largely the form that it exists today and not as a collusion contract created by publishers) had an intended purpose that was to maximize the enrichment to society that can be obtained by the society having access to diverse kinds of creative works, and offering the creators of those works some means of controlling their works for at least a limited time at least gave many of them an incentive to not resort to self-censorship as their main form of such control.
Authors really just don't engage in self-censorship as a means of control. Copyright, from an author's point of view, is a way to recoup their investment. If they can't do that, they have to have other jobs that take time away from creating. Potentially, those jobs take away all their time from creating, so they don't create. It's rare as hell to find someone who is interested in creating works, has the financial means to do so without having to worry about the cost (and opportunity cost), yet refuses because they're a control freak. I'm confident that the sorts of authors you've identified are so rare as to not be worth concerning ourselves with.
As for the purpose of modern, authorial copyright (as opposed to the old stationers' copyright), you're almost entirely right: I'd only say that mere access is not enough. Rather, copyright is intended to provide an overall benefit to society by increasing the number of works which are created and published, while imposing the fewest and shortest restrictions on the public. It operates by providing some temporary benefits (whose actual value is determined by the market) to authors, but this is merely a means to an end, not an end in itself. If copyright were actually meant to benefit authors, it's clear that it has never done a good job of it at all. The stereotype of the starving author exists for a reason.
As a side point on the matter of controlling works for a limited duration, I am compelled to add that I do strongly believe that copyright durations are far too long today, and should be shortened drastically, by no less than a factor of 2, maybe even more, and with very minimal, if any opportunities for extension.
Personally, I would drop terms to a year, with numerous opportunities for renewal, but with overall maximum lengths that were still quite short (probably no more than 20 years or so, and less in the case of some types of works, such as computer software). The reason is that when we had renewal terms, many rights holders failed to renew, evidencing a lack of desire for longer copyright on their part, and getting works into the public domain faster through their inaction. Since everyone winds up as happy as they wanted to be in that scenario, I see no reason not to return to it.
Regarding maximum lengths, you may be interested to read the following paper on the subject: http://rufuspollock.org/papers...