The first reason was simple.
The Nine Heavens Sword Sutra wasn't something just anyone could cultivate.
It required extraordinary talent in the Sword Path, and Varesh's South Sword Yang Physique and Sword Bone made him exceptionally suited for it.
Most cultivators would gain little from possessing such a special technique in the first place.
The second reason was more significant.
The Nine Heavens Sword Sutra didn't originate from the Shinayin Empire. The jade scroll stated that it had come from an organization in the Eternal Sea.
That made the relationship between Varesh and the imperial faction much more complicated.
The faction had apparently raised Varesh on behalf of that organization, which meant it couldn't simply seize his core inheritance without consequences.
There was another safeguard as well.
