I know this goes against everything you were just saying and I hate to be that guy but technically there's a rule in place that says you're not allowed 3 weeks inactivity without permission so it's more a case of systems in place not being really followed by management.
Generally speaking though I agree that things can be more relaxed. I didn't bother with warnings when I was comps manager but it was a small department so it's easier to keep things all close-knit. Then again, on the other hand, I've also seen it go the other way, when there wasn't any warnings given then staff become complacent and lazy but the latter was usually caused by a manager not being up to the job or addressing issues.