Marketing messages was a big feature at the time. The marketer would write content of the message for different channels (email, sms, chat, …) and the contacts themselves would choose which channel they prefer. And later on a AI could choose the optimal channel for each contact.
The idea was revolutionary. But I’m not sure if anyone use it. I think it’s all wrapped in the ChannelBundle so it shouldn’t be hard to make a plugin out of it. I would vote to remove it from the core and make it a plugin.