Piracy is an exception, but self interest remains a rather poor guide for proper behavior, generally speaking.
That's an odd thing to say, given that self-interest is the entire basis for copyright.
The public is self-interested; they want more works created and published, and they want those works in the public domain, where they are most useful to the public. In order to get more works created and published, they will temporarily allow restrictions on those works (where representatives of the public get to determine the scope and duration of the restrictions), so as to incentivize authors at the least cost to the public. Ultimately, the works are required to fall into the public domain. If the cost of copyright to the public is greater than the benefit to the public, there would be no point in having it, as the public would literally be better off without it (or with a differently formulated copyright law where the public benefit outweighed the public cost). The ideal copyright law is the one that provides the greatest public benefit, regardless of how appealing authors and publishers may find it as opposed to some alternative.
In doing this, the public has appealed to the self-interest of the authors, who want to make money by charging monopoly prices for their works, in order to recoup their investment and make a profit. It isn't guaranteed that they'll do so -- a work could still be a flop -- but they've got an opportunity. Financial self-interest is the only incentive that copyright can offer; while there are other incentives to create works (e.g. becoming famous, art for art's sake, sending a message to the audience, etc.), copyright doesn't matter for those.
So really, copyright is self-interest all the way down. It may only appeal to one kind of self-interest, rather than the whole panoply, and it may involve delayed gratification of self-interest, but it's still self-interest. There's nothing else at work there; it is not altruistic.
Piracy is simply self-defeating, in that pirates, who cannot stand to wait for the copyright term to end, engage in what would be lawful behavior later, but at the cost of reducing the incentivizing effect that all of the rest of society is counting on, thus reducing the overall benefit to society. Of course, this assumes that the copyright law is properly formulated. If the lawmakers have become corrupt, and no longer write the law so as to best serve the public interest alone (with whatever benefits authors receive being determined purely as a matter of what's best for society), or if social norms have changed, and the law no longer quite reflects what society wants out of it, then it may be that the law is no longer justified, and the pirates are acting correctly, if unlawfully. In that case, it's the law that needs correction, not the pirates.
In any case, though, I think you really missed the mark regarding self-interest. Self-interest is the only legitimate reason to have copyright, and governs whether there should be copyright, and if so, what it should consist of -- so as to exploit the self-interest of others in serving your own self-interest.