This is why you want reusable rockets. If you recover the rocket, you get to see if any components are suffering damage, cracking or wear beyond limits, and th

This is why you want reusable rockets. If you recover the rocket, you get to see if any components are suffering damage, cracking or wear beyond limits, and then redesign systems to prevent future potential failures. This is much harder to do if you don't get the rocket back. According to the press conference, SpaceX do get over 3000 channels of data from Falcon in flight, but that's still no substitute for examining a structure that's already flown for damage. Of course this looks like a second stage failure and SpaceX aren't currently trying to recover that, but there are a lot of common parts between the stages on Falcon, so once they start to recover the first stage successfully, I'd still expect a lot of reliability lessons to be learned.