Brain surgery is pretty difficult, I assume. It seems really precise, and if you make a slip up or two you could really screw somebody up for life. There's too much pressure! That's why I'm not a brain surgeon. Yes, that's why.
But hey, human error is having less and less effect as time goes on thanks to advancements like the NeuroArm, a robot that does brain surgery inside an MRI tube. It's designed to withstand the powerful magnets of the MRI, using the brain imaging to do very precise surgery without the clumsy fingers of hung over doctors. Hell, if I ever need my brain tinkered with I think I'd trust a robot over a human, especially one this meticulously engineered.