For one, not everyone's soul is as robust as Dyon's. From Dyon's estimate, even if it was a peak dao expert who wantonly released their divine sense, their soul would definitely suffer.
This was important in several aspects. Taking away a dao expert's divine sense forced them to rely on their base observation abilities, handicapping them. But, this was just a minor point. The most important was that the soul was the basis used to communicate with the heavens and utilize wills!
If one's soul was affected by the cold qi, there was a great chance that that individual's wills would also be handicapped.
Secondly, as long as someone didn't comprehend an ice will like Ri had, they'd be unable to efficiently dispel this qi.
