Humans usually find something that interests them and they will spend all there time learning about what interests them. I started with learning how to chart and when home PCs came out I added indicators, threw away most and settled on MACD, RSI, moving averages and volume. As years went by, at least for day trading, got rid of RSI and MACD as I just know when price is slowing down but added Bollinger Bands, just a quicker way for me to see tight markets and I discontinue trading till markets expand. But most of my signals are still chart patterns based and I learned how to chart by hand, so I never use candles.
Except for ES and maybe NQ, I use indicators same in all markets, each market has it's own personality so it has little differences that need to be learned but basically same. Like I can trade one minute NQ but prefer two minute.
People lose money for various reasons, mostly they are not ready to compete against the best, it is like a five year old playing basketball against a seven footer, people think it is a even playing field, it is not, MOST are BAIT and the few are WHALES, Whale doesn't have to attack any of the bait, whale just opens his mouth and swims. Some of the brightest people come to the markets thinking their brain will overcome experience, I certainly can't bend microwaves, but I know the probabilities of swing distance of ES in first hour of ES. And there are differences when it comes to bending microwaves, YOU are working for someone and I work for myself. So when you leave your element of safety of working for others and now all alone trying to compete against the best, YOU are getting added stress where as stress for people like me is normal day. "They" are concerned over few hundred elements of trading and I am concerned over my cat having hayfever.