Q; Salaam Why to follow sahih hadith only
A; All-Praise is due to Allah,
We should never attribute something that has no basis in Quran and Sunnah to the Prophet (peace be upon him.), or to Islam as a whole. We should take admonitions from the following warnings:
Ali (May Allah be pleased with him) narrated that the Prophet (peace be upon him) said, “Do not tell a lie against me for whoever tells a lie against me (intentionally) then he will surely enter the Hell-fire.” (Bukhari 1/106 and Ibn Majah 1/31)
Salama (May Allah be pleased with him) narrated that he heard the Prophet (peace be upon him) saying, “Whoever (intentionally) ascribes to me what I have not said then (surely) let him occupy his seat in Hell-fire.” (Bukhari 1/109)
Abdullah Ibn Abbas (May Allah be pleased with him) narrated that Allah’s Messenger (peace be upon him) said: Be mindful when transmitting a Hadith from me. (Transmit) only that which you know (very well) for he who intentionally lies about me will find his abode in Hell-Fire.” (Tirmidhi 232)
These Hadiths that are stated above clearly define that it is not permissible for one to claim Hadith that has been falsely stated about the Prophet (peace be upon him) for verily they will be judged for it on the day of resurrection..
And Allah knows best...