I don't feel like setting up the external build. I just want to pop the CPU(Ivy Bridge with integrated graphics) into the mobo, pop the ram in, and stick it in the case. Do parts really ship with high enough defect rates where I'm much better off connecting everything outside the case to test it?
No graphics card so if I need to pop it out, it shouldn't take much time.
It's not necessary, just something builders like to do to save ending up having to take everything apart if there's a problem. That way they can test each component as they go to be sure it won't be a waste of time assembling it all. Since the motherboard has the most components, it is usually most often the item that can have issues. Out of all my builds with new boards, I've probably had to RMA 10% of them.
I rarely set up a complete build outside the case. Just CPU/Cooler, RAM, graphics card.
Another reason for pre-testing outside the case, is that some of us like to put a lot of effort into cable management. That takes a lot of time to get it just right. All that is wasted if you need to disassemble the system for RMAing the board, for instance. All in all, it ends up being the builder's choice.