Revenge
You say they are "acts of desperation". They look more like acts of revenge aided by a strong belief in an afterlife.
Bowser: "This is a pox on both their houses, and I do not see any moral superiority in using tanks, helicopters and rockets to kill civilians over using suicide bombers."
There is a difference when you consider the intended targets. There is also a large chasm between an adult willing to commit suicide and sending a confused child to his death.