Imagine you replaced "software" with "civil" and everything you said remains true. I can design bridges in my home but I can't sell my services legally. Will someone buy one of my bridge designs and impelement it, especially in another country? Possibly! But that doesn't make me a civil engineer, and no engineering firm would hire me. Also, it is probably cheaper and easier for people in other countries to hire a local engineer than to use my services anyway.
Your base assumption that other countries than <your country> would not have regulation might be true at first, but probably not for long, and something is better than nothing.
I agree that people cannot be banned from writing software outright, but I think it is reasonable that in many situations it is reasonable that a company or agency is held to a standard that they only deploy software that has been produced through some set of engineering practices, similar to GAAP.
Your base assumption that other countries than <your country> would not have regulation might be true at first, but probably not for long, and something is better than nothing.
I agree that people cannot be banned from writing software outright, but I think it is reasonable that in many situations it is reasonable that a company or agency is held to a standard that they only deploy software that has been produced through some set of engineering practices, similar to GAAP.