actual purpose of reading comprehension

Dear friends and respected teachers.,

I kindly want to ask you one doubt. .that's the purpose of reading comprehension is what? ? We all know its just for improving our ability of reading. ...iam not asking that one. ..for example. ..purpose of type writting excercise is improving our type writting skill...but actually the answer is storing places of the letters in the keyboard into your subconscious memory.....like this. ..the purpose of the reading comprehension is for what ?. Is that familiarising ourselves with all types of sentence? Or that letting us to build the context of texts we read by asking appropriate questions subconsciously? ?

Why need to practice reading comprehension?
What is change happening in our mind by doing those excercise? ?