It will cut down the number of instances of waittill() and endon() for each event. If you have lots of individual files all with an instance of waittill() and endon() for all the events, this adds to the maximum number of script variables the game engine will allow. So, building an event manager like this will make it more manageable and stop server crashes.
Personally, I think callbacks are better, built out of the engine callbacks, and hooking into the game events and tracing back to certain files and folders. Callbacks require no script variables, and are therefore preferable to loops with script variables in them.