It's also often the case that a lot of the hands-on day-to-day practical things are simply not very prestigious and can't be published in a way that they will appear in the "public library" or academic journals. It's not even necessarily that people want to withhold that knowledge to reduce competition, but simply the effort of writing it all up properly is not worth it. The same time could be spent working on something that results in a prestigious publication. Of course sometimes people will altruistically draft up such things in blog posts. But then again, anything people write passes through their own internal filter of "will this make me look good?" so ultimately, you can only see the real tips by closely working with and watching with successful people.

For example many of these people may work ridiculous hours and sacrifice on their personal relations. Now try posting that on Twitter and you'll be crucified that you are encouraging unhealthy culture and you are a bad person for posting this. So most people don't bother.