You're likely interacting with SCTP every time you use a mobile phone, as it's in heavy use in the control plane of telecom networks. Outside that, not so much though.
WebRTC uses SCTP in a weird way: on top of DTLS, which is itself on top of UDP. When most people talk about using SCTP, they mean using it instead of UDP.
Yes but if my program on my laptop wants to talk to my program in my server somewhere out there, chances are the SCTP will be blocked by some piece of blinking furniture along the path.