Why Should We Teach Speaking?

Speaking is one of the most difficult skills language learners have to face.
It is very important to help students develop the right preparation for real life communication situations and the ability to produce grammatically correct, connecting sentences appropriate to specific context and comprehensible pronunciation. 
I do really think that language learning is a process of discovery. The learner develops ability to use the language for specific communication purposes. Teacher facilitates students' developments. They both work together during the process. 

We should teach Speaking to make students produce sounds and sounds patterns, use word and sentence stress, intonation patterns and rythm. It is necessary to select appropriate words and sentences according to the social setting or context; organize their thougts in a meaningful and logical sequence; language to express values and judgements, in a quickly and confidently way (fluency).
I've found the following chart that shows levels in Spoken Interaction and Production:

I believe this chart is very useful for learners to find out different ways in which they can interact and produce in the spoken way. Besides, it's extremely helpful for us as teachers, so we can create different techniques in order to develop the Speaking skill in a better and accurate way. I noticed here, why teaching Speaking is so important. 

English is that it is always accomplished via interaction, this is why sometimes, many learners shocked and disappointed when using  foreign language for the first time in real interaction: We had not been prepared for spontaneous communication and could not cope with all of its simultaneous demands.Speaking is an “activity requiring the integration of many subsystems...all these factors combine to make speaking a second or foreign language a formidable task for language learners...yet for many people, speaking is seen as the central skill” (Bailey and Savage 1994: 6-7).

FINALLY:We speak for many reasons- to be sociable, because we want something, because we want other people to do something, to do something for someone else, to respond to someone else, to express our feelings or opinion about something, to exchange information, to refer to an action or event in the past, present, or future, the possibility of something happening, and so on (Lindsay and Knight, 2006: 58).