Salaam Al-Fateh,

I can't speak for all, but I can tell you personally why I have rejected hadiths.
There are a number of reasons of course.

For one thing I do not believe that the Quran tells us to follow hadiths. I also do not believe that God would leave us (human beings) to sort through all of the so called saying of the Messenger and leave it up to us to decide what is fabricated and what is not fabricated. Just don't believe that at all.

Also there are plenty of hadiths that contradict eachother... and many people have their own version of the same hadiths aswell. Also there are many hadiths that even contradict the Quran.

Also this is word of mouth. This is what people have said other people said about the Messenger... who are we to take their word for it?

But anyways, it all goes back to the Quran. I've never read of Buhkari in the Quran. I've never read that there are other books to be followed aswell. Nope, not at all. And you've never read of this in the Quran aswell.

salaam