The thing is, the auto hubs CAUSE aluminum and other parts to break. I've seen it with Heathers truck with no locker and small tires, because they have the bad habit of unlocking when you back up to get another run at something and when you have the go pedal applied, the hub will realize that it needs to lock, and then...... BOOM!!!! Something broke.
You're right, it's not the hubs fault that the aluminum and other stuff broke with small tires. The aluminum is a bad weak spot, it breaks even with manual hubs. But it lasts longer with manuals. The autos are just too inconsistant.