^Well, actually the only problem with that is the fact that it will cause a ton of performance problems :/
When a unit leaves the map, the trigger event registration wouldn't get destroyed, and thus, you would have thousands of events registered to one trigger throughout the course of the game.
That's why Bribe's DamageEngine destroys and recreates the DamageEvent trigger every time 15 units are deindexed. (Meaning 15 units leave the map)
It also has some other features like Recursion safety and such.
If you were to damage a unit inside a trigger registered to a Damage event, you would cause the game to crash due to an infinite loop.
That's why Bribe provides you with a boolean that allows you to turn off the damage system, deal the damage, then turn it back on.