Since the Messenger of Allah left "the Book of Allah and the...
Since the Messenger of Allah left "the Book of Allah and the Sunnah of His Prophet " in order to protect people against misguidance, there is no need for any of these things invented by "Ahl al-Sunnah wal Jama`a" especially since every innovation is misguidance, and every misguidance is in the fire of Hell, according to the sacred hadith.
Rational people and the people of knowledge blame the Prophet for neglecting his Sunnah and not ordering others to record and safeguard it against distortion, variation, invention and innovation, then saying to people, "I am leaving among you the Two Weighty Things, so long as you uphold them, you shall never stray after me: the Book of Allah and my Sunnah"!
But if these rational folks are told that he prohibited them from writing it down, it will be the greatest joke, for this is not the doing of the wise: How can he prohibit the Muslims from writing his Sunnah down then tell them that he is leaving his Sunnah among them?!
Add to the above the fact that the Glorious Book of Allah, when we add to it the Prophet's Sunnah which the Muslims wrote during many centuries, contains what abrogates and what is abrogated, and it has the specific and the general, and the fixed and what is similar to something else, for it is the sister of the Holy Qur'an. But all the text of the Holy Qur'an is correct because Allah, Glory to Him, took upon Himself to protect it, and because it is recorded.
As for the Sunnah, it contains more inaccuracies than accuracies. The Prophet's Sunnah is, first and foremost, in need of someone who is divinely protected against sinning to point out to its accuracies and to reveal all the changes made to it. Anyone who is not divinely protected against sinning can never do anything of this sort even if he were the scholar of scholars.
Both the Holy Qur'an and the Sunnah, moreover, need a very highly knowledgeable scholar who is deeply immersed in their injunctions and familiar with their secrets in order to show people, after the death of the Prophet, all the issues in which they differed and the ones with which they are familiar.
Have you not seen how Allah, the Most Praised One, pointed to the fact that the Holy Qur'an needs someone to explain it, saying, "We have revealed the Reminder (Qur'an) so that you may clarify to men what has been revealed to them and so that perhaps they may reflect" (Holy Qur'an, 16:44)?