Think of it more like the patent system. A patent is just a publicly available description of your invention. You could write it up yourself and publish it to a website for $5 / mo, so why would you pay the >$10k it costs to work with a lawyer and file a patent?
It's not the description of the invention itself you're paying for, but the rights you get that make it worth it to file a patent.
In Ethereum, the "lawyers" and "patent examiners" are the other nodes in the network and the miners which enforce that the smart contract code ran as it was suppose to and can't be undone.