Started back in WW2 when the government restricted the ability for employers to offer higher salaries, so employers offered additional compensation to employees outside of salary. That coupled with today's tax incentives have made it stick.
I know that history. But it’s time to change something that made sense a long time ago but now is distorting the whole employment market, costs a lot of money and causes a lot of suffering.
This is covered very well in the book "America's Bitter Pill"