Because if you want your kids’ peers in school to mostly be from households that earn a similar or higher income than your household, the best way to do that is to move to a school district with the biggest lots and homes you can afford, thereby ensuring the population of the school is made up only of people who can afford all the space and driving.

It is literally what makes “good” school districts “good”, the household incomes of the student population. And moving to a suburban place filters that nicely. Same reason why residents will often times oppose apartment developments, since they allow lower income residents to move into the district.