I used to think like this, but after a point in time I realised I hadn't got a clue what I was talking about, either. It's something that affects different people across different backgrounds and qualities of life. It's far too easy to put it down to 'pussy mentality'. Someone can have everything; happy family life, money, then go and jump off a bridge. But because it's a silent illness with no outward symptoms people think nothing is wrong. There doesn't have to be a defining moment for it to happen, it's not a symptom of how people deal with tragedy or misfortune.
I'd say any illness that makes people want to kill themselves is pretty serious. We shouldn't confuse people who can't be arsed and want a lazy life to those who struggle to get out of bed everyday, for something that often you cannot put your finger on.