The primary reason this behavior is allowed to exist and expected to continue is that software is not a true profession in the formal sense:
https://github.com/prettydiff/wisdom/blob/master/Leadership_...
https://github.com/prettydiff/wisdom/blob/master/Leadership_...
To that end, your CV is the best license you can carry. It's unique per person unlike generalized licenses that lump people together like a hash collision.
Requiring licenses will have two effects - making people pay money, and complicating job seeking. You can gauge a bridge for safety. You can test weld jobs. You cannot standardize code writing ability. My understanding is you want the profession to remain the same with the exception of bearing an extra piece of paper to my name. What does this improve?
What I'm saying is, you're not original or clever in wanting something the industry and academia does not, and has invested in figuring out.