Over the years there have been numerous trolls who have lifted pictures from the Internet to back up their stories. Premature babies/sick children etc. These pictures have almost certainly been lifted from other blogs or websites.
Conversely other posters may post pictures of their children here which would be equally easy to lift by someone wanting to troll elsewhere.
And furthermore, we have in the past had at least one user here who turned out to be a suspected paedophile selling pictures to paedophile rings for doctoring for nefarious purposes.
Banning all pictures of children would put a stop to any of that in the name of MN.