Honestly speaking why would you play on unknown or new gambling site where you can play the same game on the existing gambling site without having a problem? One reason is that they offer something that the existing gambling site don't for instance a opening promotions like free bets and many more. Usually that's the only way they can get players and also not because the gambling site is new it cannot be trusted.
That's pretty normal for new gambling sites; they should have a promotion to attract gamblers to register. But if they are doing well, like having good customer service, fast withdrawals and deposits, and anything like that, I think they can retain gamblers to stay. However, if we have to choose, it's wise to go with gambling sites that have already built their reputation, as that's the way to minimize the risk of getting scammed.