Filing any sort of case takes a lot of time and money. That stacks the deck against any individual bringing a case against an organization, especially a large one.
Also, as any lawyer will tell you, such cases are difficult to prove. There are rarely witnesses to acts of discrimination, and when the word of one individual is weighed against that of an organization, who do you think a judge is more likely to believe?
Furthermore, almost nobody is stupid enough to say they've fired, or denied a job, promotion or tenure, to someone because of his or her race, gender, national origin or religion, even in those places where it's still legal to discriminate against, say, gays. Instead, they find--or, in some cases, fabricate--another reason. Or, if a qualified candidate "aces" an interview, the person or committee making the hiring decision will say the candidate was "not a good fit with the culture of this organization" or some such thing.
Southeastern Oklahoma State University has probably done what I've described in the previous paragraph, at least in the case of Rachel Tudor. In the summer of 2007, she announced that she was transitioning and would start presenting as female on her job, as an English professor, during the 2007-2008 academic year. She continued to work there until she was denied tenure, and terminated, in 2011. According to her lawyer, it was the first time an SOSU English professor's application for tenure and promotion was denied after a favorable tenure recommendation from a promotion committee and department chair. Moreover, according to the suit, she experienced retaliation after she had the temerity to complain.
Now, I know I don't have the full story, but there's good reason to suspect that she was wronged. I really want to find out what SOSU's rationale was for firing her.
Whatever it is, it--to be fair--probably isn't half as mean-spirited as some of the comments on the article I've linked.