Because in my personal experience - as both an interviewer and a hiring committee member - what you said is completely wrong.
> they don't count a lot of factors while rejecting a candidate, you make one > mistake on their particular set of questions, you are out.
Completely false. I have personally seen many people get hired despite doing poorly in an interview or making mistakes.
The hiring committee looks at all of the available information - resume, recommendations, and interview feedback when making a decision. There is no "one-thing" that will make or break a candidate.
> They don't even look at your resumes until all your 4 interviews are completed
I have no idea where you are getting this from. All interviewers receive the candidate's resume prior to the interview. I always review the resume's to get a sense of what the candidate has done so I can ask appropriate questions.