star wars - Why didn't the Clones use vibroblades to fight against lightsabers?

It is known in the Knights of the Old Republic series that vibroblades were made from a special material that couldn't be cut by lightsabers. Then, why aren't the clone troopers using any?

Answer

The special material which makes vibroblades resistant to lightsabers is cortosis. However, cortosis was scarce and the Jedi restricted its use:

Close at hand sat a stubby treddroid tasked with monitoring the progress of a mining probe that was sampling a rich vein of cortosis ore at the bottom of a deep shaft. A fabled ore, some called it -- owing to its scarcity, but even more for its intrinsic ability to diminish the effectiveness of the Jedi lightsaber. For that reason, the Jedi Order had gone to great lengths to restrict mining and refinement of the ore. If not the bane of the Order’s existence, cortosis was a kind of irritant, a challenge to their weapon’s reputation for fearsome invincibility.

_{Legends novel Darth Plagueis, p. 10 (emphasis added)}

Since cortosis was mostly unavailable, vibroblades were unsuitable as a weapon against a Jedi. Blasters aren't much better since Jedi can deflect blaster bolts, but at least they put some distance between the user and the Jedi's lightsaber (Jango Fett, for example, proved how effective blasters could be against a Jedi, and how important it was to maintain one's distance from a Jedi).

Finally, clone troopers and stormtroopers weren't intended to fight Jedi in most situations (especially clone troopers, who until Order 66 were allied with the Jedi). Consequently, there was little reason to equip them with vibroblades (especially since it would be far too expensive to equip an entire army with cortosis-weave vibroblades, given the scarcity of cortosis).