The fact is that depression can be "terminal". Treatments don't work for some people. If someone is suicidal and can't be helped with treatment, that's pretty terminal.
The reason why a clinic is preferable to "do it yourself" is that most of the time "diy" forces you to involve unwilling people and is often very messy. A friend committed suicide when I was in high school and was found by her sister. If they have no loved ones, a stranger will find them eventually. That person didn't ask for that trauma. If suicide is inevitable for a very sick person, bringing it to a professional is the responsible and kind thing to do.
Getting help is hard. Getting good help is almost impossible for some people. Sometimes the mental health conditions make it 100 times harder to seek that help.
I have suffered and still suffer from mental health conditions that can make life as unbearable as any terrible physical conditions. On top of that, people downplay, mock, and stigmatize invisible illnesses. Society as a whole looks down on people who can't keep up with healthy neurotypicals. The more we try to keep up, the more we neglect our mental health. And then we can't keep a job or pay bills.
Therapy is mocked openly, but is the only solution offered if medications don't work. People who need therapy are told they don't need it because of this internalized stigma surrounding mental health.
I'm safe and treatment helps me enough to get by, so despite my strong feelings I'm not in danger. But I understand the desire to do this, and I sincerely hope the world can develop more empathy for people who suffer from mental health conditions. The stigma makes it harder to recover and a little understanding and kindness to people goes a long way.