You can absolutely trust me with your private information, especially with your bank account and pin code. DMs are always open.
Besides that, DMs are useful when I wanna continue talkingto a user about a topic that came up in a thread but further talk in the thread would just derail the thread.
Or when you make a post in the community happenings thread but you fucked up a link or forgot to link to a discussion. Then I drop you a DM so you can fix it and won't get banned from the thread if Null is in some bad mood.
Some people also use DMs to work on a thread together so a cow can not DFE before the OP goes live. Not me tho bc I don't do threads but if I think you are cool user I might send you a surprise DM with some cute cat pics just because.