Research in carbon nanotubes only really matured from fundamental to applied in the past 15 years, so I don't think it's that surprising that the market isn't flooded with them yet.
We're already seeing some of the first commercially available CNT products, though. Take Vantablack[0] as an example. Or for non-commercial applications of CNT tech, see the CNT-reinforced bicycle frame that Floyd Landis used to win the Tour de France in 2006.[1]
When you consider that Bakelite was invented in 1907, but didn't see major manufacture until the 1940s, or that PVC was discovered in the 1870s, but didn't see commercial production until almost the same time, it doesn't seem like CNT are much behind the timeline for plastics. The entire chemical and plastics revolution didn't really take swing until the 1960s.
CNT probably aren't vaporware, and even if they were I don't know if that'd be too damning a story for Quantum Computers. Quantum Computing isn't "undiscovered" or "[not] proven to exist." Plenty of labs have produced physical quantum logic gates, and IBM even makes access to some of their real 5- and 16-qubit machines available online through the cloud.[2]
[0] https://en.wikipedia.org/wiki/Vantablack
[1] https://archive.fo/20120713061226/http://news.cnet.com/Carbo...
[2] https://quantumexperience.ng.bluemix.net/qx
