I'm healthy and enjoy a good walk, but I wouldn't really want to bring luggage a mile from an airport, especially not if the weather isn't nice; it seems rare for foot traffic out of airports to be particularly easy.
I walk nearly a mile (1.2km) just to get to the nearest bus stop (that buses come to often) from my airport. I only travel with a backpack though. You're right in that they don't have sidewalks though out of the airport area.
Because there are no sidewalks out of the airport. This is depressingly common. Airport designers only think about cars and busses. Maybe the train if it is near a city that has it, but even that is far from a guarantee. Usually the only access is a high speed road that connects to an even more pedestrian unfriendly highway.
Boston Logan you can definitely hop onto public transit pretty easily. But I'm pretty sure you're not just walking to anywhere in East Boston from there easily.
Indeed. Silver line (to South Station, where you can transfer further) is free to get on at the airport, precisely to encourage riding public transit out of the airport.