Suicide is a sign of depression and despair. No matter how weak or coward someone is the instinct of survival is still there. When a man believes that things can't get better no matter what he does (sometimes this is true unfortunately) then suicide seems like the only way to "free" himself.
Keep in mind that everything is relative and what looks like a desperate situation to someone might be everyday life for someone else due to differences on their social, economical and generally their living ways. The world is different inside everyone's mind.