It’s about what you’ll do on campus with the campus community. Do you plan to write for the paper? Play club sports? Organize music events?
I’d also venture that some schools that allow students to live off campus from the outset are a) happy that they are relieving pressure on campus housing and b) realistic about how they contribute.
With that said, they are also wanting to see that you too have given thought to how your experience can extend beyond the classroom. Schools that have small commuter populations have worked really hard to try to ensure that they are not a different class of student and will have the full student experience, as part of the commuter cohort as well as part of the student body in general.