[qxcv]

The problem is that well intentioned suggestions like "eat dark leafy greens" tend to sew doubt in the minds of patients, and as a result you have lots of cancer sufferers on batshit insane diet regimes because "a friend-of-a-friend said this would help"[0]. When someone is staring down death and you say "hey, I bet this would help", they're going to listen very, very intently, regardless of what a rational person might make of your suggestion.

At its extreme, this mentality can be actively harmful. I know of one person who does "spiritual healing" over the phone, charging a handsome fee to pump your telephone line full of good vibes. It may sound stupid (the cynic might even assume malice on the part of the giver-of-vibes), but things aren't so black and white when the chips are down.

[0] This wouldn't be so bad if it weren't for the fact that crazy diets compromise your ability to enjoy life without delivering any discernible medical benefit. It's all well and good to adopt a fighting attitude and say "I'm going to beat it!", but that attitude may not result in an optimal payoff in the long run.