Because at this age, spirit binders who have contracted two spirits are already a minority, not to mention those who have contracted three, that's much rarer.
After all, even if a spirit binder's level allows them to contract new spirits, if they can barely nurture one well, how could they think about nurturing a second one?
Although, there might be some whose first-born spirit didn't turn out well, so they would want to start over with another one.
However, for spirit binders, if the chief envoy spirit isn't up to par, they usually wouldn't have a second. Instead, they would just change their crafts.
So, the spirit binders who have many spirits under them usually fall into two extremes, all their spirits are either strong or weak.
The prior strength of Wukong and Xiao Bailong was clear to all four people, each being 9th Grade Soldier, far superior to their spirits.
Who would have thought they were hiding another one?