Are these answers used in recruitment much? Or are they for other purposes?
The obvious use case is where you have a large operation and you are seeking to either deploy staff within it to maximum effectiveness, or attempting to understand and resolve conflict.
It's not at all unusual, for example (I'll use IT as a specific example) to end up with someone whose technical strengths are great, but whose ability to identify a strategic direction is weak, operating beyond their competence in some areas. That can result in problems, as the individual themselves can struggle to perform, despite their undoubted strengths in some areas, which results in them feeling crap about themselves/the job, and quite possibly annoys the hell out of those they are directing, not to mention those who they report to.
Tests like these are a useful screening tool to be able to identify traits which might present problems, and which can therefore be addressed through training, coaching, or redeployment. Ideally, it's done as a collaborative process, so the metrics are discussed with the staff member, and some kind of agreement reached on the best way forward.
As ever, the art is in how they are used - getting a MBTI classification for someone and then simply deciding what they will do purely on the strength of that is, not to put too fine a point on it, just shit management.
Personally, I see these things as handy shortcuts, with all the limitations that implies. You can get a far richer sense of someone's capabilities by having a series of conversations with them (although even there such frameworks offer a useful way of structuring the information gained from those conversations), but that can often take resources that a company is unwilling to devote: getting an executive coach in at £300/hour, for 3 hours each, in a department of 30 senior managers is £27,000, which could well be value for money in terms of the business's bottom line, but might be a scary amount of money to spend for what might be an intangible result, for example. And that'd be a comparatively cheap coach.
And the other thing is what you do with the results - it's one thing being able to say to a staff member, "you're an ISFJ" and read the blurb at them, but actually working out with the person what that means in terms of their work role is a much more nuanced business.
