It was designed by telcos for telcos; I don't know if they ever got around to using it. It can't be used in the normal Internet because it doesn't pass through NATs.
You interact with it every day if you use a cell phone. The control plane of the nodeb/enodeb(or "cell towers") and further into the core network in UMTS/LTE is using SCTP. Control messages for voice calls and SMS is carried a top of SCTP. Control plane interconnect between carriers for roaming is done over SCTP.
(Though there's still plenty of gear still using TDM or ATM)
