Earlier quoted context omitted.
SCTP is a superior protocol, but it isn't implemented in many routers or firewalls. As long as Comcast / Verizon routers don't support it, no one will use it. It may be built on top of IP, but TCP / UDP levels are important for NAT and such. Too few people use DMZ and other features of routers / firewalls. Its way easier to just put up with TCP / UDP issues to stay compatible with most home setups.
Why do the routers involve themselves at the transport layer? Can't they just route IP packets and leave the transport alone? Firewalls -- whose firewalls are we talking about here? If a client (say, home user) tries to initiate an SCTP connection to a server somewhere, what step will fail?
Because they have to do NAT, at least on IPv4.
> Firewalls -- whose firewalls are we talking about here? If a client (say, home user) tries to initiate an SCTP connection to a server somewhere, what step will fail?
Because the connection tracking that's needed to even recognize whether a packets belongs to an outbound or an inbound connection needs to understand the protocol.