I don't know anybody who constantly makes money in trading on the stock exchange or in casinos, or at bets! So I think that daytrading and gambling can easily be called similar..
I don't think there is someone who can earn daily in betting or casinos. AFAIK, we don't always win in each attempt in gambling. While in trading, you can earn daily if you don't target too high for profits. On the other side, some gambling games such as dice or slot, require no specific skills since they are luck-based. In trading, especially in day trading, we need specific skills to optimize the chance of profits. You cannot trade with careless skills & no knowledge in trading yet it will lead to losing only. So, how can we conclude they are the same?
If playing Texas HoldEm Poker and other gambling games on Facebook consider as a gambling game, I think some of my friends can earn money. But I don't know how much they can win, and I don't know if they can buy their daily needs or not. But I admitted that it is so difficult to make money from gambling, whether it is online or offline, and not all people can successfully get the win money. Maybe people prefer to do trading as they can have the chance to make money, although that will depend on how the market moves.