Why is there no cure for most diseases if we understand the cause?

Let's think: The existence of a problem does not imply the existence of a solution. I can know how I broke an egg, but all the king's horses and men can't put it back together. The same is true of a gunshot wound, and of most diseases. Cures are effected by surgery, by meds that kill microbes, and by procedures that remove or incapacitate cancer cells. The rest is palliation or waiting for self-healing.