Why organize a labor union to keep the tyrants from paying you poverty wages when you could just submit the name of the tyrant to the assassination market and let somebody take care of it?

The more unpopular you are as a human being, the shorter your expected lifespan, because the reward for you not existing would increase proportionally to how much of an asshole you were.

What are some ways that you can think of where a scheme like this could have undesirable results?