The problem is thinking that there could be such a thing as a license for software engineers in general. That would be crazy, almost like having to be licensed to write English. Software is applied to too many different domains and tasks.

What could work would be licensing for software engineers in certain specific domains. For example, we could require election systems software engineers to be certified for that field. Same with automotive software, power plant software, etc. etc. I agree that we should do this. But it's going to apply to only a small fraction of all software engineers, because licensing Web app developers is not practical.