I'd like to also add to this that SCTP doesn't ship on Mac OS X either by default. Although, in recent years there have been development on an SCTP over UDP standard, allowing for user-mode SCTP. Yet, I still haven't seen a mature version of this API ship on Mac OS X.

Some time ago, I also did performance testing on SCTP vs. TCP. It's surprisingly sad how much worse SCTP's performance was compared to TCP. I imagine that this is because just isn't as much work put into SCTP as TCP.