I suspect the apostrophe is going to fade away over the next century, precisely because nobody seems to know how to use it. Newspapers and book publishers still seem to use it correctly, but as you point out, Hammer Head, schoolteachers seem to be all at sea, and they're the ones teaching the next generation of journalists and publishers. It's a shame when English teachers are illiterate (and this goes right the way up to university tutors, as I can personally confirm), but that's progress for you.