I think there are really scam sites but it's only a few but not all. There are sites which are transparent with transactions and you can check them legitimately. Also, friend referrals are a big help (especially if you trust this friend not to bring you to harm or be scammed). I guess you will know if you’re being played when you start to question the methods and once you have noticed a pattern.
That's certainly true, mate. It's always advised to check on a specific online gambling site before placing your bets on it. Some are fishy as they don't provide information related to bets placed by all the players, their bankroll, etc. However, others are transparent, which results in confidence from gamblers within a specific gambling site. There are many reviews available across the web which you can find related to gambling sites which accept cryptocurrencies like Bitcoin or even traditional ones which accept fiat.
While scam sites are usually associated with the acceptance of cryptocurrencies as the only medium of exchange, that's not the case, as there are a few which are truly legitimate (like the one under my signature). For greater transparency, reliability, and fairness, smart contract-based gambling sites are far superior than traditional online gambling sites. The probability of such games becoming fixed is very minimum due to the transparency of the blockchain. If you suspect that a specific game is not fair, you can always check its source code. The only downside related to games which rely on smart contracts, is the high fees of the blockchain network due to scalability limitations.
However, once they become perfect, then they could easily take the gambling industry by storm. Nevertheless, there are a huge variety of gambling sites nowadays which are provably fair and have little chances by being fixed by their owners. Just my opinion