Despite the MCAT being "the great equalizer", there's still many factors that contribute to a score... Your interviewer is probably trying to understand some of those. Consider:
1.) An individual's ability to focus completely on the MCAT
2.) Ability to take a course, get a private tutor, etc. (these things can cost $1000-$5000+)
3.) Having other life commitments like kids or homeownership interfering with your MCAT studying
4.) Employment commitments
It's well documented that a higher SES correlates to a higher MCAT score. From a previous thread here:
-Applicants who are most socioeconomically disadvantaged (SES A) have a significantly lower average MCAT score (23.4) than those with the least disadvantage (SES D, 28.3)