I enjoy how private and shareable the content is. When someone reaches out, I can often point them towards the stack overflow conversation where they can get an answer or continue the conversation.
It allows productive collaboration between siloed teams and breaks down some barriers, culturally and bureaucratically, that hold orgs back. Fast and easy documentation and solutions if utilized properly.
The company is getting bigger and the devs working on our kernel are just too busy to answer to all (recurring) collegues' emails, chats, etc... SO4T is the best way to get in touch with them to ask for clarification about specific issues not covered by our standard documentation (and of course there're plenty of those) and spread the answers company wide.
Another main purpose is to discuss about guidelines, abstract concepts, wish list (in some way) with the one that are in charge to lead the developement of our products.
A plus is of course the common interface shared with the standard StackOverflow that we're all used to nowadays.