It's to lessen the potential impact of a breach. a) you have a chance to recover from a hack in that two hours, b) it can reduce the speed with which leaked data gets to the opposition, and c) it reduces the likelihood of a hack getting valuable data.

And these are just a few reasons I can think of. There's nothing but benefits to this policy and very small negatives.

It's analogous to filling the moat before a battle. It's just a defense intended to slow an enemy. Try to remember that these guys are some seriously strategic thinkers, they're not morons and they're not technophobes.