Answer
Because the weightings differ. IIM Sambalpur gives work experience 20 marks out of 100 while IIM Indore gives Class 12 alone 25. IIM Calcutta awards up to 6 points for a non-engineering background; IIM Sirmaur awards 5 for an engineering one. The same CAT score against different profile weightings produces genuinely different outcomes.
Question
Why did I get a call from one IIM and not another?