They are not physical items.

Tangible resources like a knife, car or real estate has a physical presence that can be held in one's possession. Doing so, it is not available for others to be used. If you grow wheat on a parcel of land, I cannot grow rice in the same space.

If you manufacture something intangible like content, process or recipe, there is no physical presence to possess. They are a form of knowledge. Knowledge can be replicated without end by any who are interested in doing so. Your mastery of calculus does not stop me from mastering and benefiting from it. Your use of the Hall–Héroult process process in your business doesn't stop me from dying the same in mine.

Society attempts to protect those who are interested in producing these intangibles through the use of copyrights, patents and trade secrets.

Without these forms of protection, those ideas would be immediately free to be used. This was the situation before laws implementing these protections were out in place.

With both copyright and patents, the deal is essentially the provision of a limited time monopoly before those intangibles are free to be used by the public without compensation - the "public domain". The idea is that the creators have an opportunity to monetize their labor in the near term while society stands to benefit from the new or recombined ideas over the long term.

By choosing to create intangible products, the creator is in effect agreeing to the terms and conditions society offers.

If these creators are not happy with a limited time monopoly offered then they are free and able to place their work product directly into the public domain.

They are also free to choose other industries to participate in. Nobody is forcing them to make music, write books, research processes. Yet apparently they see sufficient immediate benefit to do so so.