When you interview someone for a job, or are helping to interview someone for a job, is it rude to ask why they're interviewing in the first place?
Sometimes the answer is easy like "well my company is laying off a thousand people this year and so I've decided to move on" or "they've decided to get out of software development and instead make candles"
Sometimes it's the safe middle road like "well I feel I've taken my career as far as it can go in my current job..."
But sometimes the answer could be something that throws up a red flag like "well I can't stand my boss" (could this person be a problem employee?) or "I didn't like Technology X" (well we use lots of Technology X here...) or "I don't like staying in a job for more than six months..." (well, we were planning on hiring long term...)
On the one hand, setting off a red flag can keep you from hiring the wrong person - on the other hand it could also be a false positive. You might wind up not hiring the best employee ever just because he had a total slimeball of a boss and couldn't contain himself, for example.
Is it appropriate to ask why this person is looking for another job? Or should you just not worry with such a thing?