Here's one reason why
The other reason is that it turns out that one half of our cluster is apparently cursed. I'm not kidding. Seriously. The boxes are identically spec'd and installed (although I didn't do the install, so who knows). If we run on Server 1, we run about 1/2 the speed and capacity of Server 2. So at some point this weekend probably I'll go in and rebuild Server 1. Exactly how I wanted to spend my weekend.