> Since when has protected speech required being valuable?

For this specific topic in the US, it's necessary. The third prong of the Miller Test is "Whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value."

The three-pronged Miller test is for examining if something is obscene, which is a considerably narrower criteria than whether or not a given piece of free speech is worthy of protection. Speech does not need to be 'valuable' to be worthy of protection, it needs to have a specific lack of value as determined by the Miller test to not be protected. Big difference.