That seemed staggeringly high, considering that Google's is less than 10%. So I asked her how these legal firms managed to pull off such a high interview success rate. Apparently, they only ever invite someone to interview, if they are already pretty sure they want to hire that person. And how does that work? They make no attempt whatsoever to judge your competency on the basis of interview performance. Rather, you are judged almost entirely by your resume - the "brand name" of the law school you attended, your GPA, and the "brand name" of the law firms you've previously worked at. If your school or previous law firms aren't prestigious enough, you won't even be invited to an interview.
In fact, not only is the above a convention, it's often a firm policy. My sister once got a job offer, through very fortunate circumstances, at an elite law firm. But their HR department blocked her hire, literally because she did not attend a top-15 law school.
Ironically enough, I've never heard anyone complain about legal hiring being broken. Perhaps that's precisely because legal firms don't even give most people a shot - they are filtered out entirely at the resume stage. I imagine people get far more agitated when they are rejected after an interview, as opposed to being ignored entirely from the outset.
I'm personally glad to work in an industry where even the most exclusive companies are willing to give everyone a shot at the interview, regardless of which school they went to. Is hiring broken in tech? Sure. But it's completely dysfunctional elsewhere.