Shao Sisi, Xia Wuque, and the five other people could all be regarded as some of the most powerful cultivators of this galaxy's younger generation. If the seven of them teamed up—no, three of them would be enough—they would be able to look after two people each, yet they would still have quite a good chance of carrying their remaining team members through the tower.
The trial in this tower was probably similar to the trial of the stone statue formation. Those at the Mountain River Tier definitely wouldn't come across dangers at the Sun Moon Tier. Otherwise, that would be an execution, not a trial.
To them, bringing two people each wouldn't pose a problem.
The reason for their gathering was in order to get to know each other. After all, they were all destined to enter the Majestic Heaven Sect. At that time, the advantage of their backgrounds would drop significantly. Thus, it was advantageous for them to acquaint themselves with more prodigies.