Nothing gives me greater pleasure than having someone chamber my thrust only for me to overhead chamber their chamber and slicing their face of. I agree with you though, chambering is useful. I find it very effective against pikes and 1h spears. Still it's mostly a duel technique, I wouldn't bother to learn to chamber decently if you don't enjoy dueling.
That's the thing. In duels a lot of people expect to be chambered and often manage to block it. But in battle servers it's a death sentence if you pull it off. They are never ready for it
Yeah it's easier to do in controlled environments so that's why I think it's situational. I rarely do it. And when I do it I am either desperate or reckless enough to risk it, or have enough armor to afford being hit in case I miss