Well, for me, I've never seen martingale as a strategy to be honest, and that is because I because it's not one.
Strategy should help a gambler win, whether he or she is lucky or not, but in this situation, the martingale way of playing Slot only ensures that you take more and more risk, and at the end of the day, you still have to depend on luck to win, and if you are not lucky, you did lose your entire bankroll even before you blink your eyes.
Any thing called strategy; where after applying it, I still need to depend on luck to win, rather than depend on how good the strategy is, then that is not a strategy, and to this effect, I once again say that martingale is not a gambling strategy, but more of a style.
Exactly, these are not strategies but merely betting patterns that people apply to try and recover their money when they start losing, and most of these patterns tend to put the gambler in more danger because if you are losing $0.5 per bet, you would be losing $16 after 4 to 5 bets or so if you are doubling the bet amount after each loss. You incur a loss streak, and as you rightly said, the bankroll would be over before one realizes it.
I have always said that, betting patterns, or strategies if you call it that, are recipes for disaster. A gambler might not lose much if they gamble normally even after incurring a loss, but if they start applying a pattern after a loss, they are inviting the house to feast on their money in that case.