The other major factor is fault tolerance. Software has bugs, and hardware breaks, but that's accepted. Programmers in industry have invested a lot of time in r

The other major factor is fault tolerance. Software has bugs, and hardware breaks, but that's accepted. Programmers in industry have invested a lot of time in routing around the problems. That buys time for human operators to get paged and fix things. For every major outage that makes the news, there are thousands of smaller problems that users never notice because of CDNs, failover, graceful-ish service degradation, autoscaling and/or overprovisioning, and fallbacks. Services can be reliable even when the software and hardware that backs them is not. In other words, "reliability" is a property of the whole system, including the human operators, not just the code. The code can actually be pretty bad, yet the entire system can still be reliable in terms of being available and functional when the users want to use it.