you must always have confident on your bets, but never overdo.

No. It's not wrong. It a game for adults and is welcomed almost everywhere in the world in one form or another.

Gambling is not wrong itself. The lure from obtaining something without effort is always there and that is why gambling is so attractive. If you go only for the fun, risking a little bit hoping it grows by betting, then it's not a problem. In the other hand, if it becomes an addiction, it would be better if you forget about it.

Yes, you are right. Gambling should be for fun only, if you are addicted towards gambling then its wrong and just need to stay away from it.

Maybe I didn't use the right way to say it. Gambling as an activity is neither good or bad. The consequences that people has to face because their gambling habits are. I have family and friends that think that all the games are rigged. Nevertheless, they keep playing again and again, waiting to hit jackpot someday. Are they out of their minds throwing their working earned money by gambling? I don't criticise. I gamble sometimes too, even with my engineering background tells me that the odds are against me every single game. It's my decision to do so and in the way I feel like having fun.

That it correct. These sites are designed to make profits for them self not for players. If most of the players start earning profits from these sites then how these sites can survive for long time and how they can spend money for advertising their service?

They know finally they are the winner in this game so they spend so much money for advertising to attract more people to their sites.

there is no initial point , what if you won ton of bitcoins on the next session ?
then again lose on the third session ? its just luck and there is no long run thing..until you die.

Sure it depends on luck. but there's also a difference in house edge's with games/sites. The lower the edge, the more chance you have to actualy win something/or lose less

Most gamblers are bad at math. or just dont care to lose.