The distance between Azure Fragrance City and Grand Sky City is simply too far. Although the entire place was under the Four Seasons Valley, the distance was inconvenient for daily transportation to Azure Fragrance Realm.
Therefore, there used to be a grand teleportation formation that directly connected the Four Seasons Valley and Azure Sun Realm.
However, when the Pale Mountain Abyssal Monster corrupted the imperial spirit veins of Azure Sun Realm, the elders back them simply dismantled the teleportation formation in Azure Sun Secret Realm.
They were afraid if anything went wrong, the monster might directly escape to the main sect. To minimize the damage, they destroyed the teleportation formation, severing the connection between Azure Sun Realm and Four Seasons Valley.