The primary argument for this would be transparency to combat wage discrimination.
Personally I would just want to know it for negotiating purposes.
i find glassdoor to be a great resource for salaries. for large companies, i always see my role represented with enough data to even compare what the salary should be by years of experience (not just a blanket average for the job title).
super small companies probably won't be listed, but you can still see the similar roles in your area, get a range of pay, and negotiate appropriately - lower the target some if you're not experienced or if you're working at a small company, ask for the higher end at a big company, etc.
having everyone's salary published still wouldn't be more helpful as things like being a top performer would make someone more deserving of higher pay. you got idiots who will see the highest salary for the role and ask for that with no consideration for how many years the person has been there, their performance, and to be honest, their connections/politicking.
there are tons of resources for salary data that can give accurate information on averages in your area, that's all you need to negotiate.
Nah. I'm good. 
...was only askin for clarification
