There's a huge bias towards the happy case in specifications, user stories and so on.

I try hard to discuss error cases, but often I only get a very unenthusiastic "well, show an error message, d'oh" as a response, which wears me out over time.

This is worse for non-interactive things, like event handling. There's no person to show the error to, usually logging and aborting are kinda the only possible actions, which is endlessly frustrating.