Why do players avoid the concealed hand? I know...it's hard when you can't call...but the advantage is that you CAN'T expose...so others have much less idea what you're playing. And you don't have to think about calling during play. BUT...you do have to keep track of how many of your tiles are going out!
Now, I didn't say they DON'T know what you're playing....they could have some idea. If winds are going around in the passing...and they don't get thrown when play begins, someone is keeping them.
Maybe a concealed winds hand.
OK...so you usually need a couple of jokers for a concealed hand...to make up for those discards that you can't call. Unless you're doing a singles and pairs hand, which is always concealed.
Just be careful not to expose 3 winds.....a sure giveaway that you've exposed a pung in a concealed hand! You're DEAD!
PS: Tonight the doctors introduce a new class of beginners to the game of Mah Jongg! What fun!