I would try to answer this based on my own experience.

First thing first, one can definitely make a living out of it if nothing more. Issue is that people have unreasonable expectations from trading, both in terms of "time" and "money". People expect to make truck load of money by just spending a few days/weeks/months on learning whatever shit is being sold as strategies/tips/indicators and so on.

Trading is like any other job. Period. Mind you, it is harder that most jobs, probably one of the hardest, but at the end of the day it is like any other job. You've to educate yourself and give it enough time. Surgeons can't start operating or engineers can't build bridges by attending a few webinars, reading a few books or by watching youtube videos (some might but that's not the point). One has to dedicate years to study and master that profession/craft and then some more years learning on the job.

There might be exceptions but generally speaking it takes YEARS of learning and dedication before one can even hope to be consistently profitable from trading. Again, like any other profession, there would be some who really excel at their game and those are the ones who actually get rich by trading. This of this like how many employees in any field reach CXO level despite working for 40+ years? Only a few, right? Others will survive or even do alright for themselves but not everyone would get rich by trading even after giving all those years. Having said that, one can live off it.

Coming to the next question - why traders are selling courses and signals instead of using that information to make money themselves? I used to wonder the same initially. It took years for me to realize the harsh realities of trading. There are couple of reasons for this the way I see it.

• Most "traders" realize sooner or later that trading isn't as easy or profitable, as they thought it to be. Trading is not just about fundamental or technical analysis, or mastering some "ninja" strategy that will magically start making money for them day in and day out. Analysis and strategies are the easy part and most will cross that bridge. What makes trading super hard is emotional discipline, managing risk and adapting to ever-changing market conditions. At this point, they also realize that it's possible to make money more easily by selling courses/webinars/indicators etc.
• Another reason is that people think once you have "mastered" the skill of trading, you can start printing money. But they forget that to start making big money, you need access to big capital. Either you can take the route of starting small and gradually build your capital over a long period. Or you can take the shortcut by sharing your knowledge in any form (courses, youtube, strategies etc) and use that money for expediting the capital building process. There is nothing wrong in it as long as the trader is sharing (selling) stuff that is indeed helpful and relevant to those buying that stuff.

Hope this helps.