But how often do interviewees showing up with gross clothes, swear, or be rude to interviewer?
I'd say almost 0?
"Yes, you have to shower the day of an interview."
"It's never acceptable to pull out your lunch and eat in the middle of the interview, please don't do it again."
"Yes, you have to wear something other than the shirt you slept in."
Part of my friend's responsibility was to give feedback to the interviewers. Her students were passing over MS to go to Google, despite MS offering significantly more for a salary. Their interviewers asked her for feedback to figure out why. She had to politely say that Google was seen as cooler. (The cooler impression wasn't just the image gained from the interviewers, it was the problems Google was trying to solve. But, the interviewers added to the company's image of "coolness".)
She held this position probably a decade ago and left after a few years. Things may be different now.
It's so simple you wouldn't expect people interviewing to fail it, but it still happens.
It's definitely higher than that. It is a pretty easy thing to avoid, you'd think, but some people fail.
