1. Lure you into buying their bogus system
2. Convince you to sign up with a casino of their choosing so they can earn commissions for every referred player.
Scams come in many forms. The most inventive scam includes elements of both selling you a system and having you sign up with certain casinos. These scams 'get you' both ways. Be cautious of anyone that says things like "Having a good roulette strategy will make you serious money"