Cultivators begin dealing with the Heaven's Augury Mercantile Union as soon as they step onto the path of cultivation, a necessity no one can avoid.
Take Lu Ye for example, not long after he entered the Spirit Stream battlefield, he started buying and selling goods through the Heaven's Augury Mercantile Union. It's true he could also trade with other cultivators, but that's not as convenient and cost-effective as doing business with the mercantile union.
If one can't do business with the Heaven's Augury Mercantile Union, many things would become complicated.
The lower a cultivator's cultivation, the greater their reliance on the Heaven's Augury Mercantile Union. The union's decision brought trouble to those two Ten Thousand Demons Ridge sects, and it was no small trouble.