Because then a single firmware bug could wipe you out. Once the drives all hit 4500 hours or 700 bad blocks or some other trigger, they die. It's happened bef

Because then a single firmware bug could wipe you out. Once the drives all hit 4500 hours or 700 bad blocks or some other trigger, they die. It's happened before. Could also be caused by bad grease, or shoddy bearings, or pretty much anything. There is security in diversity.