One reason is to prevent rival sects from ambushing and killing on the way, resulting in death before the competition even begins.
Another is a matter of face.
All the family sects send Golden Cores, and anyone who doesn't will lose face.
Most of the Heavenly Prides have Foundation Establishment cultivation, with only a few being Golden Core Cultivators. These Golden Core Prides are also considered strong contenders for the top three positions.
When the time came.
The entrance to the Heavenly Pride Secret Realm would appear at the very center of the square, and then the scenes from inside the Secret Realm would be projected in mid-air. Surrounding the square, tens of thousands of seats had been set up for visitors from various sects and families to watch their Heavenly Prides' performance inside the Secret Realm.
