Racism! Saudi Deaths Matter! I Can’t Blow Up!
Even the Kamikaze pilots of WWII fame had to wait their turn to try to fly a plane into the mid deck of Allied combat ships.
The Japanese considered one of their better tactics, as it threw an abiding fear into the Allied seamen, and it called forth the spirit of dedication and sacrifice among many of their young.
Which is apparently the same kind of camaraderie the ISIS commanders are trying to instill in their young recruits.