The "how likely is it, really?" response to questions of technical correctness has always bothered me. It takes a mindset completely alien to mine to say "Here's a race condition. Sure, it's undefined behavior, but the race is narrow, so it's rare" or to say "Sure, memory allocation can theoretically fail, but in practice almost never does" or to say "fsync is too slow and most computers have batteries these days".
Software is unreliable enough as it is due to problems beneath our notice. It seems reckless to avoid fixing problems that we do notice. Sure, you could argue that rare problems are rare and that users probably won't notice them --- this attitude is penny-wise and pound-foolish, because you can't meaningfully reason about a system that's only probably correct.
