Source: p 287, Sweet Reason: A Field Guide to Modern Logic (2010 2 ed) by Henle, Garfield, Tymoczko.
Predicate is the reason we started on deductions. In Sentential, remember, we can verify that an argument is valid by using truth tables or the short-cut method. With Predicate, we have no such tool. We can show that an argument is invalid if we exhibit a universe in which the premises are true and the conclusion is false, but (until now) we have had no means of showing that an argument in Predicate is valid.
In the 2 Logic textbooks read (the above and Hurley's), from the given premises, no exercise will ask you to determine the conclusion yourself; instead the textbook divulges the conclusion and then asks you to deduce it. But this is irrealistic; real life, one must determine conclusions oneself.
So without computers, from given premises (that may be long and convoluted), how can you conjecture, before deducing, the conclusion yourself? One must at least conjecture a conclusion before attempting any deduction or (dis)proof.