The reality that to much stuff in networks (mostly firewalls, NAT and other middleboxes like that) only understands the basics (TCP, UDP, random bits of ICMP) and drops SCTP. You can do SCTP over UDP, or use it in networks you can control and fix, but not reliably as-is over random internet connections. So we now have HTTP2 and other protocols now reinvent parallel streams instead of swapping to SCTP, but that's how it is.
SCTP is alive and vell in very niche applications. SIGTRAN [1] for example is an adaptation of middle layers of SS7 network stack that runs on top of SCTP/IP.