how is requiring a BA legal?

How can so many employers require a BA degree when that degree is not free and available to all citizens?

There is no program that ensures a student can achieve a BA, indeed the postsecondary drop-out rates in the US are the highest in the industrial world, and college is not free as it is many other countries. Many qualified people cannot afford to go to college.  And colleges favor those who are able to stay in school longest, i.e., wealthier kids.

So exactly how can so many employers require a BA degree, often for jobs that used to require a high school degree, which was, at least, available to every citizen?  These employers are requiring citizens to pay for training that isn't free, is available on a discriminatory basis and is, in fact, quite expensive.  How can so many city, state and Federal agencies require this training when a path for many citizens is not available?  In positions funded primarily by taxpayers, how can this degree be required unless the state provides a path?