Each of these situations is different from each other even through they have a lot of similarities.
Having people tell you they want you to shoot them isn't that uncommon, nor really common I had three in my 33 years on the job.
I shot none of them why because they were unarmed and didn't pose an immediate deadly threat. I also was highly trained in excellent physical condition and very sure of my abilities to handle the situation with out shooting.
I am sure some, not all of these shootings, are because some ,not all are because the officers are not sure that they can handle the situation with out shooting.
If you take an officer who has let their training, physical condition, skill levels slip or just their physical size IE and over weight or small officer. They have less options then one that is up on his game.
But I also know of one case where the person making the claim shoot me should have been shot but wasn't until he killed one officer and crippled another. He was armed making threats and really wanted to commit suicide by cop.
All these situations are highly volatile and each one different one can't be judge by what happen with another.
I can tell you this that each one I handled if any of them would have pose an immediate deadly threat to me or other officers I would not of hesitated to use the proper amount of force to stop the threat.