Why should you be entitled to the mental labor of others? What good is it to spend years studying and doing work in a field if one can’t charge more specifically for that knowledge and experience?
Your concerns are valid, yes, but only if you value money over self-accomplishment.
I learn skills for myself, not for others. It's about investing in yourself, the output is not necessarily money. You can learn dance classes, it'll never pay-off, but you'll feel more accomplished.
Furthermore, from my perspective, money is unfair and is not a reflection of social value.
Because not the most deserving people are earning the most (the farmer who feeds others, vs, someone sharing pictures on OnlyFans).
I often speak with people who are smarter than me, and they share their knowledge with me for free. One example is for machine learning. In return I do share my other discoveries in fields I know better.
In the short-term, it looks better to keep the knowledge secret. But in the long-run everybody benefits.
The others still have their knowledge, I have new knowledge, and together we can build something better.
I'm very grateful to people who share what they know without charging me every minute like if I'm on a phone sex-line.
And the best lessons are actually free (YCombinator, Bill Gates, Physics classes, etc).
If you want others to value self-accomplishment over money, maybe they decline because they can't pay rent with self-accomplishment.
You're effectively criticizing people for not giving away their investment for free.
Also, you mention that money is unfair and is not a reflection of social value? What is the social value in being a lock smith? If you spend most of your day working as a lock smith for "social value", then you're expecting others to do the same. How does it work when you need something from someone else, but they "don't have the time" or just don't feel like doing it. "Social value" has less actual value than a social contract, but... getting back to money being unfair... Money is a way to pass value between entities, be they people or companies or other. I will pay money to a lock smith (again, just using a random previous example in this thread) and he will use that money for something he needs or finds value in.
Value is also highly subjective, hence the widely varying prices people are willing to pay for things or services. Though, as long as there are enough people willing to pay for a thing or service at the given price/rate, then it will be sold for that price/rate.
One last note, when it comes to information, which is not the actual work, I think you're underestimating the value gained by the person appearing to give the information away. On the internet, if you're writing articles for free, based on your experience, that you also sell to your employer as "work", you're probably getting something else out of it as well. Maybe recognition, hoping for a better job, or maybe just gaining experience in writing.