Local governments impose licensing requirements on some professions. This is not something the professions just voluntarily impose on themselves. (If they did impose it on themselves, there might even be antitrust problems as a result.) This is mainly (or at least purportedly) for the protection of public health and safety, not to make it easier on potential employers interviewing job candidates.

It actually has nothing to do with job interviews, because every such professional needs a license in order to practice their profession, even if the professional is a self-employed entrepreneur.

So to be clear, when someone asks for software engineer licensing, in effect what they're asking is for local governments to regulate the ability to practice software development, even for self-employed programmers.

And then you can expect a visit from the government software inspector.