So today I was stowing some gear and one of my handguns was in a case. Before I put it into the safe, I reflexively racked the slide even though I knew the gun was empty.
Clink, a round was in the magazine and chambered.
Now because I am not Alec Baldwin, everything was fine. I was treating the gun as loaded, as always, had it pointed in a safe direction, as always, had my finger away from the trigger, as always. But the gun I knew was unloaded had a round in the magazine.
That is why we check every single time. Better to verify a gun you know is unloaded a hundred times than think that a gun is unloaded when it is not. Don't get sloppy or lazy, not ever.