Because the level of ignorance, stigma and confusion surrounding mental illness is immense. Someone I know joked about bringing extra ammo with whenever they took me to the mental health clinic. I told him not to worry, most of us would just want to shoot ourselves. Things got /real/ quiet. I honestly can't think of a whole lot positive that I got out of my rough background (aside from being a resilient motherfucker, and really good at diving for cover at the sound of bullets and explosions).
Even something as 'simple' as depression or addiction is massively misunderstood. Throw in the fact it really does vary a lot from person to person and things get really muddy. It's not like I can just not be depressed, but it does take a lot of effort for me to get going. And I know that's the thing I need to do, even if it feels like I'm rolling a boulder up a hill with pelvic thrusts. It feels vaguely weird knowing one's condition is being used as an exercise in analysis (hurhur, anal).
Cruel as it sounds, sometimes one does have to detach from a mentally ill friend or family member to save oneself. It's rarely intentional on the part of the ill person, but that's how it goes. Sometimes that's the impetus that gets one going to get help, sometimes not. Sometimes, I have to stop talking to my friend with a mental illness because she's worked up, which gets me worked up and suddenly we're two mixed nuts flailing around. A lot of people just don't know how to handle a loved one or friend with these kinds of illnesses (including addiction).
Have a shell for a heart. 
