...which can often be "the hotel I booked doesn't have the reservation, and I'm currently SOL". My wife and I booked a rental car for a trip through one of the many booking sites (Expedia, probably) and when we got there, the company that had been booked with was gone and they didn't have our reservation because it was a totally new company. But nothing told us about that, we only learned about it when we got there. Thankfully, people are generally understanding and they were able to get us a car for the same price, but my wife basically had a panic attack due to there being other mishaps on the way. (and she's the type of person who plans things months in advance and changes to the plan are very distressing to her)

So yes, "one thing" might go wrong out of the 10,000, but that "one thing" can cause a literal panic attack. I don't have sympathy for companies that create crappy software that barely limps along and causes a lot of distress to my wife over stuff like that, or not telling us we need to pay extra to book seats on an airplane in advance to be able to sit together for a 13 hours flight. No sympathy at all.