>>16720619 (OP)because neurostimulation (using electricity on the brain) is very risky and used as an absolute last resort. why is it risky? because the brain is so interconnected that you could easily make things alot worse for the patient. one misstep in the procedure and your patient now suffers from seizures or some other shitty outcome. since we aren't sure how to cure tinnitus then it makes neurostimulation treatment even more risky.