Lack of available test tissue might be slowing down drug approvals, but the main reason we don't see cures is that drug companies don't want to sell cures, they want to sell chronic treatments. If you cure a person you have a customer on Tuesday. Treat their condition and you have a customer for life. Drug companies aren't motivated to produce cures any more than Nike is motivated to sell each person exactly one pair of shoes. This is a very good reason why public health should be publicly funded and publicly distributed. When medicine is an expense instead of a profit center, we'll start curing diseases instead of maintaining them.