Because that is the way government likes it.
When everyone is able to clamor for government favors, it empowers more and more expensive government.
If you have a valuable skill and do not like your working conditions, you should be free to shop around. Same with the company.
When government gets involved, everything goes bad.
Except that the “company” often has far more leverage than a mere jobseeker, especially in a bad economy. When there is so much disparity in bargaining ability, the disadvantaged party needs some help.