It's also the case that it's incredibly hard to test things like battery life, wifi connectivity and the effects of heavy processor workloads in a systematic way. You hope that your vendors do a good job (and I bet Microsoft's contract with Intel involves penalties for these major defects to try and incentivize Intel to handle these).

Look at the first Iphone4. How did they miss something as simple as skin contact causing significant antenna interference? Most of us hit it immediately. The answer: hardware in the real world is really hard.