It happens a lot, unfortunately, for multiple reasons. First is ordinary power loss, then the fact that Rpi comes with no power button so people get impatient a

It happens a lot, unfortunately, for multiple reasons. First is ordinary power loss, then the fact that Rpi comes with no power button so people get impatient and yank the power (ok, that’s not unexpected, but corruption is), and then Rpis have long been known to be finicky with their power requirements. In the latter case, I've seen it happen from a too-long USB power cable. One can argue about whether those reasons are in the "but the user should know better" column, but when they result in a corrupted filesystem, they nevertheless add up to a poor user experience. Hope one day the Rpi has easygoing power requirements and a button you can push for orderly shutdown.