Question is why they rejected them, especially since the Dead Sea Scrolls indicates those books were very much in circulation amongst Christians ca 100BC and have to date existed amongst Ethiopian Churches (one of the earliest churches still in existence)
The men running the WT, (Governing Body, and perhaps others) are not so much interested in finding out what the truth is, but instead more inclined in CREATING THEIR OWN TRUTH.
A good example of this is their latest teaching regarding "THEIR IDEA" of how the resurrection is going to proceed.
A gay person that dies gay will be resurrected gay and little by little the gay will be removed depending on his progress in obedience.
There is no biblical information or other ancient historical references alluding that the resurrection will proceed in such a way.
Everyone has a certain way of extrapolating information from the past, and this is how these men work in dispensing their theological views upon their members.
The members love their ideas and continue to support the information they come up with.