Every time you wager, the chance of having 20 consecutive loses is only 0.00014%.
You may think that's very good. Right? But the more you play, the more chance you have to hit 20 consecutive loses.
Yes, at first glance, it may seem like a small chance, but in fact, such a long losing streak can happen in almost every game session. Personally, I have had 20 or more losses in a row many times when playing dice. That's crap, especially when you rely on a Martingale strategy.