A homeopath and his wife allow their infant to die a slow and tortuous death of infection due to severe eczema, because they believe homeopathy will cure her, despite repeated warnings from doctors.
A woman eschews medical treatment for her breast cancer, opting for The Secret and a quack’s ideas about acidity causing disease. She dies.
Lots of people believe that alternative treatments will extend their lives or even eliminate their cancer, and some of them give up entirely on conventional medicine. It’s one thing to decide that the cost of chemo is too high and make an informed choice to live as well as possible. It’s quite another to rely on alternative treatment to save you, then die anyway.
People go to a chiropractor to get pain relief, but may wind up with a fatal stroke,
Or the chiropractor might tell the person to stop taking her medication for epileptic seizures, resulting in her death.
People take “dietary supplements,” which are practically unregulated by the FDA, and wind up dying, or if they’re lucky, just going into liver failure.
This isn’t to say that conventional medicine is risk-free. But typically there is a good chance a remedy will actually do something beneficial that will balance out the risk. With alternative remedies, usually the most you get is placebo effect. Sure, regular medical practice is not always actually evidence-based, but at least that is the goal. With alternative practices, there are no standards whatsoever, and perhaps more importantly, there is no mechanism for improvement. There can’t be when proponents take a “heads I win, tails you lose” approach that rationalizes every failure and lauds every apparent success.
For more examples of the dangers of woo belief, see Whatstheharm.net.