They've long ago abandoned the pretense that the Sunday "public" lecture is for anyone but the initiated JW, anyway, what with the speakers' frequent recourse to "theospeak," i,e. JW-only jargon like "circuit assembly," "pioneering," "unbaptized publisher," "Faithful Slave" etc., etc., blah, blah, ad infinitum, ad nauseum.
You gotta wonder whether they really want the public at meetings anymore, so they might as well lock the doors, as long they'll let you out when you wanna barf!