@loveyoutoomuch-
It's because pms on here (like any dms) have been used as a tool to gr00m min0rs on this app. The pms aren't as regulated as the message board so that's why people's dirty dm rps haven't been confiscated in the past.
They originally would dodge the question but there was an article published about the gr00ming problem. Although they say that it's because no one uses it, that's not entirely true. Just an addition to the predatory behavior. Which makes sense for some part but what sense does it make to take dms from a story/community building app? Like if they began taking comments from Instagram stories, kinda.