I do think that many gamblers are aware of the odds and that the casino has an edge over them. But where else can we have these kind of chances to make a profit? So if we play dice and do 50/50 bets, sure the chance of winning is not exactly 50%, but more 48-49.5%. These are pretty good in my opinion, because we can work with them. We know before hand of our chances and can bet accordingly. If we trade on the stock market for example, we don't know the our odds. We might thing we are having a great deal but it could be that our chances of making money are only 30%. Same goes for the payoff, we never know how high a stock is going to rise.
As for the stock market, there are scientific studies (they are possible since the entire trading history is available) that show that shorting on average is unprofitable and buying is profitable.
Can you share the links to the studies, or where did you get that information? Because I've encountered the opposite: that short selling, though very risky, is more profitable. You just have to be an experienced enough trader. Of course, for a newbie, who doesn't yet see how the stock market functions and some general tendencies, can't expect certain price values it must be difficult, but is it unprofitable for the skilled traders as well?