Wherefore suicide bombers?

Reading another depressing article about suicide bombers in Palestine, I have to stop and wonder what makes the suicide bombing of a great-grandmother more newsworthy than that of the more typical young bearded male. Are the lives of Arab women somehow more valuable than those of Arab men?
Even more puzzling is why the suicide bombing of an older woman, whose life is winding down, is portrayed as in some way more (rather than less) disturbing than that of a younger woman with everything to live for.
Not that there is that much to live for in Palestine, one of the most systematically downtrodden and impoverished ghettoes on this bleak earth.
I find it all but impossible to get my head round the concept of suicide bombings, though. However grim things may appear (and I fully admit that I am unable to imagine just how grim things must appear to a destitute Palestinian), I am still not sure how a 68-year old mother of nine thinks she is helping the cause of her family or her town or anything by blowing up (or failing to blow up, in her case) a few Israeli soldiers.
This is not some spiritual statement about her religion such as the warriors of Islam purport to make (however misguided, and however contrary to the teachings of their faith, they may be). This is just about desperation, and about revenge for its own sake.
Hamas may have, at root, a just cause. But sanctioning, and even encouraging, this kind of behaviour is clearly irresponsible and self-defeating.