Because we are tightly connected to the augmentative communication community, we get to see beautiful examples of AAC making communication possible for people almost every day.
But as time moves forward there are more and more examples of people who use AAC to communicate even though they CAN actually speak.
There are many children and adults who are part-time AAC users. Often, they use AAC in stressful situations or when they feel overwhelmed. Sometimes, individuals choose AAC when they are uncomfortable or when they are meeting new people. Others lean on AAC because their speech is not always clear to those that don't know them well. Some people use AAC to reinforce messages that might be misunderstood otherwise. (a bit more about being partially verbal here)
The realm of AAC support reaches far beyond those who simply cannot speak.
(Notice we didn't say those that have no "voice." We firmly believe everyone has a voice inside them, AAC just makes it possible to more easily be heard.)
Not long ago, I met a nine year old girl who has full verbal communication. She has no trouble expressing herself with words. Her family has AAC in the home for other reasons.
This young lady has mild anxiety and she has found that when expressing concerns or frustrations to her parents it is often easier for her to do it through AAC. Yes, she is perfectly capable of speaking out loud, but using a device as her voice lifts some of her anxious concerns and makes it easier for her to say what she is really feeling.
There is not one, blanket reason why people choose to communicate using AAC.
I recently sat in an online session with a man who is multiply disabled. He is in a wheelchair and does not have control over his arms and legs. He is able to vocalize "yes" and "no" but he also communicates clearly with his eyes using AAC.
His comments and questions were poignant and well crafted. While he IS able to vocalize a little bit, without the aid of AAC it would have been hard to fully understand his thoughts and suggestions.
While we often think of AAC as the go to solution when a person is unable to communicate verbally, we should also remember that AAC could be a perfect aid to support speech in a person who has use of vocal communication.
Can a person with a broken leg get around without crutches? Yes, but it would be much more difficult and maybe even detrimental to that person.
By that same token, can a person with some speech communicate without AAC? Yes, but augmentative communication can give them the opportunity to better share their message and be more clearly understood.