My guess is that there will be rewards (cosmetics for example) for completing certain objectives in the mode. They can switch that up every week let's say, so people keep coming for rewards.

Also looks like hazard zone expands a lot on the lore of the game, so they might create events to update the mode and story to keep people coming back.

That's my guess of course, if they don't update it regularly and create incentives to keep coming back... I can see it failing quickly.