Martinfail is never recommended to players, but those who are new in gambling and think they can outsmart the casino by methods written on the internet which have constraints that cannot be fulfilled in reality. They forget that the casino is running for years and have been making profits for many years too from the players who lose more than win.
Martingale doesn't always fail though and I am living proof of that. It's a useless strategy in the long-term and will suck up your bankroll quickly, but it's actually pretty effective in the short-term if you play smartly.
For example, Rollbit duel arena is a good place to execute this strategy in the short-term thanks to zero house edge.
Martingale is not a strategy, I will repeat it again that martingale is not a gambling strategy, it does not increase one's chances of winning any game, both in the short of long term.
Do not mistake your being lucky and winning while applying martingale to your gambling, as that it's the martingale that helped you win, it's absolutely not..
What martingale does is, it increases your potential winning amount, since it has to do with increasing bets on each round that ended in a loss, and we all know that in gambling, the higher your bet amount depending on the odds of the game, the higher the amount of money you win if your roll or bet won, martingale does nothing when it comes to determining when you should win or lose, that's entirely up to the casino or luck, martingale only helps increase the amount of money won if you are lucky to win while applying it.
I hope this is clear enough.