Reasons why people keep secrets were already told. Groups keep secrets to lure others. Individual keep secrets in order to feel more important than others.
Some people see gate keeping and speak out against it. It is a noble belief by itself, but it completely misses the point. Even if we exclude the severe danger that some things can be over long period of time to a practitioner...
(people like talking how spirits or spells might kill them, but they won't be writing that if it really was that dangerous, wouldn't they?)
...there are other reasons why people will never understand some things. I like to go back to story of tower of Babel and when God had cursed humanity to speak in different languages. As a result, this tower had collapsed due to our inability to communicate with each other. I like to think that it was not the different languages which are our curse. That thing is trivial to overcome. However, the real reason is that we cannot find common ground. Despite the fact that we all born and die as equals. Despite the fact that our souls might inhibit this realm for countless generations, from lowest beggar to highest king. Despite that we all have same universal needs and desires. There is this discord between all humans where we seemingly want to kill each other. Each convinced of their own righteousness and truth. We are unable to find universal common ground despite being same beings. Despite wanting same things. We are seemingly locked from understanding each other's point of view no matter how hard we might try. This is the real curse put on humanity which prevents us from ever being great, unified and speaking in one voice.
There is an invisible barrier which people have. Many schools of thought see this barrier as a need for ''enlightenment'' in one form or another. I do think that this ''enlightenment'' is a way to remove those obstacles put by God. Practitioner which had dabbled with magic directly in one or other form is forever changed in a subtle way. His view on the world usually changes dramatically when he completes his transformation, his or her enlightenment. I had read many stories of old WF members who in their words had went insane during this process until they come out of it stronger. I do think that there are countless more who never go through this process, get stuck with all the downsides of it with none of the benefits.
What I had noticed through the years is that people are stuck in a thought pattern which prevents them from seeing how things are. They want you to give something how they want to be given. They want it to look how they imagine it to be. They want it to be easy. There are so many issues which prevent sharing of knowledge between us. I tried to help some, but they are seemingly stuck in their world. My words fall upon deaf ears. One member for example kept demanding me to give him sources to magic books which would help him to achieve results which would be easy to objectively prove and was very upset about me when I did not gave him any. All of this misses the entire issue. You cannot just take a book and learn how to cast spells. You need to learn so many subtle things first. How to meditate. How to breathe. You need to learn patience. You need to learn how to concentrate. You need to learn humility. Even I, mighty Calicifer are incredibly humble in my own ways.
Most people will lack something in them to effectively share this knowledge. When you meet someone with whom you can share this knowledge, in my experience both practitioners already know what they are doing and they are unwilling to take up foreign methods seriously. We pick and choose parts which we like and adopt it in our own discipline as we see fit.
If you want my secret through which I had achieved all my incredible feats, here it is with no obfuscation:
A lot of energy work throughout long periods of time. For me it might take days of channeling my energy, twisting my perception of the world around me and willing something to happen. This energy work can be either incredibly intense through burning, raging emotions or cold and persistent through many days. If working with entities, be humble, be persistent and authoritative. My super secret trick is to gather enough will power for a ritual and simply say to the spirit that I'm not going away until you address me. That usually saves both of us a lot of trouble.
Here, it is all that here is to it for me. I need no book. I do not need any incantations. Rituals are not necessary, but they do make things more straight forward and easier to get results with. So, now as you know secret to everything, does this allow you to meet spirits? Heal your own wounds? Destroy your enemies? Or do you need so much more context to achieve all of this on your own?