Yeah I'm also curious. When I was at Google there were a list of things you were never supposed to ask a candidate because that's Super Illegal(TM) and could expose the company to lawsuits. That included sexual orientation and marriage status. That was more than ten years ago, I'd expect most IT companies would do the same by now, at least in the US.
I've never been asked this sort of question at a large company. Mostly "startups" (scare quotes because they're not Silicon Valley startups; think Orlando or Chicago instead).
They also tend to ask a lot about things that might sound innocuous, like hobbies.
If I was being stupidly honest, I could talk about my involvement in the furry community. Most furries (~80%) are LGBTQ (versus ~3% to 5% of the base population).
Instead, I make vague allusions to being a gamer. (I play video games less than anyone I know, but it's not zero, so that's still technically true.)
The annoying part is that you are essentially cornered, being either LGBTQ and/or furry is a large part of your identity and it is hard to have to divorce yourself from that for the purpose of getting hired. Companies really need to get over this desire to know more about the private lives of their employees during the run-up to being hired than they are willing to disclose about their own affairs (such as: financial health of the company, maturity of leadership, attitude to quality of life issues, health care and so on).
There are ways to ask those without being illegal and these are employed quite frequently. Essentially any kind of probing into someone's private life should be off-limits.
> There are ways to ask those without being illegal
Strictly speaking, its not illegal to ask the question. However, because it is illegal to base hiring decisions on it, asking the question is legally dangerous in two ways:
(1) Asking the question in an employment interview is evidence which can tend to support that you intended to use it in a hiring decision, and
(2) The interviewee answering the question is evidence that you had the information, and thus the opportunity to use it in a hiring decision.
As a result, the usual legal advice is to strictly avoid asking the question: you can’t legally use the response, and by asking it you make yourself unnecessarily vulnerable. The idea that it is illegal to ask the question is probably a consequence of this.
