Indeed, Martingale really works but not for an extended period of time. The problem is, when a gambler gains momentum using Martingale, they start thinking it’ll work all day. They don’t consider that even with a big bankroll, a 20 straight red or more is still possible. Or maybe they do know, it’s just that they stop caring once they feel the momentum, and that confidence turns into greed.
A series of 20 or more losses in a row can happen literally from your very first bet because everything depends on luck. So, it's worth noting that the martingale strategy sometimes doesn't really work on short distances, and I agree with you that it's pointless on long distances.