It is not that they are not smart enough because they have lose so much bitcoin or money in gambling, it is just they are not lucky enough to win in gambling. Gambling is a very risky game and we all know that, but yes, you are tight that someone are doing gambling just because of profit and that is I think the only reason why most of us are gambling to multiply our bitcoin. Some of us are doing gambling just for fun because they don't know what to do anymore to their bitcoin. Maybe they have too much bitcoin on their wallet that's is why they are risking some of it on gambling for some fun. But gambling is not really recommended to do to grow your bitcoin because once you started gambling, it is hard to quit doing it especially if you already lose some of your bitcoin.
You are explain about gambling very well, But you know the thread is about "How to play gambling in a smart way"?
About the OP, i don't think that many peoples are playing gambling in a smart way, they just play it, and how can we play it in a smart way?
In my opinion, should use limited amount in every bet, and play that game, which you think you can play it very well and make money.