Studies of deaf children who are not exposed to a formal sign language indicate that the children spontaneously produce their own signs, called home signs, which emerge in development at the times of typical language milestones. however, the children relying on home signs are limited in that

I believe the answer is: they do not advance beyond the telegraphic phase of language

During the telegraphic phase of language, we would learn to differentiate longer and shorter words in order to determine which one is more efficient in the current context. Deaf people tend to unable to pass this since they never heard how long and short sentence sounds like.

answer; ///the declaration of independence;