They don't know how much they are willing to offer. You wouldn't get much out of a salary answer like this: "Each interviewer grades you as 1 to 5. We sum that

They don't know how much they are willing to offer. You wouldn't get much out of a salary answer like this: "Each interviewer grades you as 1 to 5. We sum that up, then multiply by $10,000." Even knowing the number of interviewers wouldn't help you very much. You'd need to know how well the interviewers would score you, which won't be determined until after the interview.