Those are the lavatories for the premium plus and economy cabins so even if there were a curtain it would likely wind up left open by a couple hours into the flight anyway.

But long ye not for what is not there: US airline 'curtains' are not terribly useful to maintain compliance with FAA cabin visibility requirements -- even if there were one there you likely wouldn't notice anything beyond the rattle of the clips as it's opened and closed. They have less isolation than a cheap hotel shower curtain.