Here is why: Testing is fastly becoming adopted by everyone in our industry, why? Becuase you cannot afford to not write tests if your system is large/important enough. However our current testing methods cannot not prove the absence of bugs, as Dijkstra is fond of saying. So the best we can tell our clients currently on the bug-free/security question is this: "We wrote it according to X standard and wrote tests to cover those cases.". Formal methods allow us to prove a system is bug-free/secure. It is the evolution of testing. I do not know how far off it is, but because we have already adopted testing I believe formal methods will get adopted as well.