For starters, the event indicator on the world map is buggy. You think the event is up but once you get to the area, there’s nothing.
This may have to do with the fact that it takes around 20 minutes or so for the event to come back up after killing the disciple (which in my opinion is too long).
A lot of the times, people don’t want to wait for the event to start again, so they’ll do the activities to loot the chest for the week and move on to the next thing.
This is detrimental because all that shard farming and chest looting basically goes to waste.
By making the event timed, I think you at least give people the choice to wait for the event to start and fill up the bar more quickly.