There are plenty of cases where there is no real medicine. In many cases, all they can do is administer painkillers. Take a bad joint, lower back pain, migraine. In a good percentage of these cases, placebo works really well. If you don't believe me, ask a specialist. Pain specialists (trained doctors, mind you) often prescribe homeopathy, biofeedback, acupuncturing and the like, simply because it works.

Also, long time medication is rarely desirable. Treatment gets less effective, there can be addiction issues and not least of all, it's expensive. This is particularly important for chronical diseases.

If placebo, in whatever form, helps some ten or twenty percent of people (and it does!), why not try it?