Under a hypothetical licensure system, companies would be more than welcome to hide rockstar Chad from the local CS department. They would just, for example, be more liable for damages or something. We can think of all types of licensure schemes, with all types of consequences. What makes you think software engineer credentialing will automatically work out poorly? Moreover, have you also considered its benefits? Oftentimes the world exists in shades of grey, where a system has good parts as well as bad parts. Lawyer credentialing, for example, isn't perfect, but it's better than nothing at all.