If it was a genuine attempt to die, why do they keep not succeeding?
That is exactly the issue, and part and parcel with whether or not it is a "genuine" attempt to die. People become suicidal and attempt death, but a persons brain also has a subconscious defence mechanism that thwarts that.
If you look at the statistics for suicide attempts, women are most likely to try pills. Why? Double edged sword, they can't stand physically hurting themselves, they don't want physical marks on them if it doesn't work, and the biggie... is that the chances of someone finding them and high, AND, the chances that the tablets taken have the potential to kill in large doses are usually slim.
Again... subconsciousness is at play whether you know it or not. There is a reason you can't drown yourself without the aid of something to hold you under that you don't control, such as a sufficient weight and inability to escape the attached device. Your brain otherwise forces you up to breathe.
Attempts ARE exactly a cry for help. Notice how I used the plural, not singular. Either or are a cry for help... a cry that something is wrong and the person wants to die, but they also want to live... they're just unsure which it is exactly.
Those who succeed first time, they aren't within the unsure zone; they're clearly in the wanting to die and they don't let anyone know about it. They plan it, they ensure there are no failsafes or ways out during when the brain fights back to survive. Jumping off of a building, for example, removes all such things for people. Whilst it is said half way down they will change their mind, thus their brain is working against their conscious desires, there is nothing they can now do except impact and die.
Attempts is absolutely a scream for help... probably beyond cry for help, but scream!