Want to set up an IRC client? Sure. What's the server and port name? Got firewall rules set up? That's complicated, and easy to get wrong. Your own IMAP email service? Same.
Want to set up Skype? Just sign in here. Want to set up Gmail? Just sign in here. Want to set up Slack? Just sign in here.
No regular person used a chat client until MSN Messenger and Skype came along. Nobody. Now they all use the messenger service built in to Facebook, and they don't even think about it.
It's just way easier, even for technical people.