It is interesting that you bring this up, it is widely know that many of the books which contain trading systems are created by people that do not trade and that earn their money by selling books about how to trade, if you took the time to backtest their systems you will realize that they lose money on the long term, but those people know that people will not take the time to verify who they are or to tests their systems so they can get away with their scam and no one exposes them for what they are.
And what is wrong in teaching someone from your friends your own profitable trading strategy?
You did not read my response, what I am saying is that many of the books out there about trading are sharing strategies about how to beat the market but those strategies do not really work and are not profitable, now while at first glance it may seem as if there is nothing wrong with teaching your profitable strategy to others, if you have one to begin with, the problem is that most people cannot remain silent about it and eventually more people will use your strategy, and as more people use the same strategy to earn money the less effective it becomes.
I think that it would get to a point in life where you didnt even need to Pay attention to people's strategies, because I believe that as you study deeply on trading, one would realize that strategies come to one naturally, I usually tell most newbies that wants to trade that they should forget about strategy first, those who develop strategy didnt learn it because you cant learn strategy, you only use you experience to come up with strategies which means without experience, you cannot have strategy and the only way experience can also come into play is when one has a very sound knowledge about cryptocurrency.
I like to expose myself more to understanding of trading and the more that I understand some deeper things about trading in crypto, the more strategy comes to me.