Inv'ation Req'd

Oh my gosh! I just had an amazing insight into the inner workings of the English language! How come people use abbreviations, like "req'd" for "required", but don't pronounce it that way, and instead say it out the long way? For example, for the word req'd, you'd say rek-ED, or just REKT. And we could have more of them, for investigate, you could have inv'ate said in-VATE. It doesn't make sense to me. Why not just give your mouth a rest and shorten it?