MAD is about as simple as it gets, but it is not "the absolute most basic type of summary statistic." In many statistics courses, it is not taught at all, so it

MAD is about as simple as it gets, but it is not "the absolute most basic type of summary statistic." In many statistics courses, it is not taught at all, so it's perfectly possible for someone to know how multiple regression and random forests work but to have never before heard of quantifying spread in any other way than with squared deviations. Just because someone doesn't know something that you do know doesn't make them stupid.