I'll be very up front about this - I've spent probably 10% of my life in various stages of suicidality, something I thankfully no longer suffer. Of course, there are many reasons why people might commit suicide, but I think calling suicide "cowardly" is not wrong so much as it is entirely missing the point. When you reach the point where you really, really are ready to do it, you really aren't living in the same world as everyone else anymore, and ordinary, normal means of perceiving the future don't exist. I don't know how else to put it except to say that, by the time a person gets to that point, it doesn't feel like suicide is a decision the person gets to make for themselves, any more than the rising and setting of the sun is a decision they get to make. It doesn't feel like it's something you are going to do, it feels like it's something that is just going to happen, and the only choice you have is "how", not "if."
EDIT: Based on my experiences, I think a lot of the "cry for help" or attention-getting suicides are actually mislabeled. It is possible to feel like you have no choice about whether or not you commit suicide even if you don't want to die. For some people, the only way to get out of intrusive suicidal thoughts [http://vicarioustherapy.blogspot.com/2009/09/diary-of-obsessive-or-intrusive.html] is to try to do it. If you don't actually want to die, you do a bad job of it so you can be retrieved. This may not make any sense to anyone whose never felt genuinely out of control in some fashion, but I was ready to kill myself just so I could stop compulsively thinking of killing myself.