Which is frankly horrifying considering the reference implementation was released in FreeBSD 7. That really ought to scare people from purchasing any of those routers/firewalls that don’t support it.
It's not a matter of time in the wild, it's a matter of adoption and cost priorities. Until the past several years, most SoHo routers were super constrained wrt CPU, memory, and ROM, so adding support for a new transport layer protocol would involve an unacceptable cost increase in what has rapidly turned into a race-to-the-bottom commodity industry.
So you end up with a chicken-and-egg problem: router manufacturers aren't going to add support for it unless there's sufficient demand, and there can't be sufficient demand because very few people can use and rely on it.
So you end up with a chicken-and-egg problem: router manufacturers aren't going to add support for it unless there's sufficient demand, and there can't be sufficient demand because very few people can use and rely on it.