They don't care, because they're operating under the assumption that it's true. According to his account, they're not putting their most private photos there—they assume that anything they post may be made public in the future.
While I will save that debate for another day, it is safe to say that when photos are “leaked” or when there’s controversy about security on the app, we honestly do not really care. We aren't sending pictures of our Social Security Cards here, we're sending selfies and photos with us having 5 chins.