Water heater in close with wall ajoining breaker panel?
The circumstance is a persistent pinhole leak that sprays the wall wet for an extended period of time until the drywall becomes saturated and crumbles.  And most people say "I would spot that immediately", but having seen a few water-heater leaks, real world, most people don't for weeks.  And then take more time dealing with it.   

Also, you would know it was urgent, but the next occupant may not.  

Remember the scene in Breaking Bad where he ignores the leaky hot water heater until the floor rots out? 

Honestly, I would use two strategies: 


mount the hot water heater below the service panel.  You don't want water near your service panel, but water doesn't flow uphill.  
build a hardback false wall set on spacers several inches (like 3-1/2") out from the wall, so there's an intermediate gap.   The false wall would stop short of the floor, put a drip pan under it.  Water sprayed onto the false wall can only run down to its bottom then drip into the pan.    (make sure the spacers stop before the bottom of the false wall so streams don't detour onto the spacers).