It's a shame really that a very promising technology does not yet reach its full potential. Hopefully very soon in the near future it will has more take up due to its promising potentials for modern networks concepts including Zero Trust Architecture, BYOD and IoT [1], [2].

[1] Does SPB Mean “Secure Path Bridging”?

https://gestaltit.com/tech-field-day/tom/does-spb-mean-secur...

[2] Extreme Networks Stealth Networking & Hypersegmentation:

https://youtu.be/vwBfqTyZLzE

The control plane software took years to develop and I think the vendors wanted to charge a fortune for it (comparable to MPLS or Metro Ethernet licenses) but it didn't provide that kind of value. SPB was more telco-ish while data center vendors favored TRILL; this standards war didn't help the situation. By the time SPB/TRILL would have been ready, people had already moved on to hypervisor VXLAN over a plain IP underlay.