Interestingly enough, many salaries are public, specifically H1B salaries:
Many Washington state employees salary info is public, including full name:
Many Washington state employees salary info is public, including full name:
So folks who do not know any better could still work for 1/4 the market rate.
They may not address price transparency for people who receive equity compensation, but it is still a great start to help those at the bottom.
But alas making it mandatory is not the way to go.
This implies some do. So it didn't answer the question.