One thing that really depends on one’s location–when I lived in Syracuse (city, also diocese), there were about 20 parishes just in the city I lived in (even more when you took in the nearby suburbs). Even if each parish dropped to a single Mass per day, there’d be multiple times in which one might be able to get to Mass, and depending on where exactly one was, there could be multiple parishes in walking distance from one’s home. It seemed hard to imagine how anyone wouldn’t be able to get to Mass on a given day.
Here, there is one pastor for two parishes and only one Mass at one parish and none at the other (but if it were still a day of obligation, there’d be a vigil Mass at one of the two parishes and at least one Mass per parish on the day itself. This is the only Mass in the entire county today. Next nearest place is about 15 miles away via 2-lane highways, and thus would need a lot of advance planning (knowing what time the other parishes might be celebrating their Mass, knowing how long the route would take, if there are any issues like road closures between here and there, etc). It suddenly isn’t so hard to imagine how it might be too difficult for someone to get there.