> By license I mean the current Leetcode interview process except you do it once and are good for at least five years

Some companies do seem to be offering something similar to this, see CodeSignal's general coding assessment or back when TripleByte was big a few years ago. I think the problem is that even within the specialized topic of LC style interviews, many companies don't agree on a similar strategy when it comes to types of questions and difficulty. There isn't one standard that every company agrees on, so most have their own flavor of it.

Yea, think of it less as a "government issued license allowing you to do software" and more of a certificate that says "I recently passed a level $LEVEL leetcode grind, you only need to test me for specialized skills or for a level greater than $LEVEL." If it actually worked and couldn't be gamed/cheated (good luck with that), it could reduce interviews to a simple check of domain knowledge not covered by the certificate.

It is already a massive waste of human potential to overstress leetcodes.

I'd rather have candidates studying unit test design, debugging, security hardening, technical writing, localization, or pretty much anything else that comes up more often in practical development.