All systems are based on the laws of averages. If you flip a coin you know it ll land heads or tails, but you can t predict which. If you flip that coin 100 times, chances are it ll land heads 50 times and tails the other 50 times, but in streaks and chops, not in neatly alternating fashion. Because no one can predict the outcome of the next spin, a systematic betting strategy will usually outperform random guessing. Roulette is a mechanical game.
System play eliminates guessing or emotional decisions.
Your play becomes as mechanical as the game itself. The ideal roulette system aims to maximize winnings, minimize losses and let you leave the casino with more money than you came in with. All systems promise to do all of this, except they fail for various reasons. Some are way too complicated, some require too large a bankroll and some are simply too boring to play. Casinos win not so much because of their advantage in percentages, they win mainly because they play their own version of a system.