If you are only betting for fun and losing money does not matter then why not, you will have a lot more wins than you have losses (overall). So that can be fun. The problem is that using a Martingale strategy when you lose, you will lose everything, wiping out all your previous gains as well as your whole bankroll. Using the Martingale strategy in the long run is a terrible investment strategy that is guaranteed to lose 100% of your money sooner or later.