1. Those damn read receipts
    I don't want people to know when I've read their messages. I also stress out when I know people have seen my messages and aren't responding to me. (I have first and second hand accounts of those things causing relationship strife!!)
  2. There's no desktop app
    So I go to facebook.com when I want to send/check messages but then once I'm there I get distracted and start browsing. I know I can go to messenger.com in my browser instead but a standalone app like Messages or WhatsApp is still so much better.
  3. People messaging me there are mostly guys who don't have my phone number
    Otherwise they would be texting! P.S. If you've asked for my number and I told you to use Facebook Messenger...