Many people think of speech therapists as a profession that only specializes in teaching the accurate production of speech sounds in words, phrases, sentences, and conversations. While articulation therapy is one aspect of speech therapy, that is not the sole duties and responsibilities of a speech therapist in a nutshell.
First things first, the correct terminology is Speech-Language Pathologist, established by the American-Speech-Language-Hearing Association. However, speech-language therapist and speech therapist are used interchangeably. Perhaps it's easier to say the latter of the two than the first title.
Many people do not see or understand the importance of articulation therapy. Learning to hear and produce individual sounds-phonemes are vital ingredients in achieving good phonological skills, these skills are most important in learning to read. Phonemic awareness and phonological skills are essential tools in literacy and language. The smallest unit of a word, which is a sound, changes the meaning of the word. If a child does not or cannot hear or say sounds correctly, he may struggle in his academic skills. The child may demonstrate difficulty in learning to spell and sound sounds out to form a word. In this case, articulation may be warranted to help the child strengthen the necessary skills needed for emergent literacy or to master literacy skills. Therefore, articulation therapy is very valuable for a beginner reader who may have difficulty producing sounds in words. Moreover, not only is articulation therapy aiming to help improve a child's speaking skills so that he may effectively express his 'needs', 'wants', and 'ideas' within his environment. Articulation therapy/speech therapy can help children in all aspects of human communication as it may improve a child's cognitive ability, making them more aware of various language components, in addition to spelling, reading, and writing.
Most speech therapists aim to improve developmentally age appropriate sounds in error to at least 90% accuracy. We know no one speaks perfectly (a goal set at 100% accuracy would be ridiculous), but perfect practice helps to get you close and this is why we aim for 90% accuracy. A speech therapist can help children maximize their communication skills to communicate effectively within their environment. The creator of the universe created us into the image of Him and if he is perfect, we should aim to be close to perfect in everything we do.
Chances are, when someone tells you their child is in speech therapy. The child is receiving more than speaking rehabilitation services. The child could be in therapy for one of the following problems: apraxia of speech (incoordination of speech musculatures), fluency disorder/stuttering/cluttering, voice disorder, ADHD/ADD, dysphagia (swallowing difficulty), etc. The problems and disorders mentioned can have an adverse affect on a child's articulation performance.
When should you worry about your child's articulation skills? According to Charles Van Riper and Robert L. Erickson, you should worry when "speech is impaired and it deviates so far from the speech of other people that it (1) calls attention to itself, (2) interferes with communication, or (3) provokes distress in the speaker or the listener". (Charles Van Riper and Rober L. Erickson, 1996).
Speech therapy is more than sounds in words!Perfectly Speaking, The Dynamics of Speech Therapy