>>13120517Number of reasons depending on the application. There's no real difficulty in fabricating them, chemical vapour deposition is relatively simple compared to other modern synthesis techniques, it's just very hard to achieve a low dispersivity in tube lengths, widths, and chiralities (how the tube is "wrapped up", there are multiple ways to do it).
In bulk materials the reason is largely that it's not cost efficient to manufacture at scale for the improvements in material properties they might offer, and also environmental concerns about mass producing a novel material and putting it in everything.
In electronics, the dispersivity in chiralities is a huge problem. Certain configurations are metallic, while others are semiconducting. Until a cheap method of isolating only 1 type of nanotube is developed, these things are restricted to experiments with experiments of top down fabricated, molecular scale circuits.
