There is no rule (lobbied-for or otherwise) that says that publishers can put publicly-funded research behind a paywall. That they can is simply a result of the fact that all creative works are copyrightable, and people are free to publish copyrighted work on freely-negotiated terms.

If you asked the public "should there be a special law excluding scientific articles from copyright protection," I suspect most people would say "no." Sometimes the public agrees with the general principles of a law, but disagrees with specific applications. In those cases, we give precedence to the legal principles, not the public's opinion on a specific situation.