"... then we'd have access to a small on-base house, but there wouldn't be a lot of work for him there. He'd have to get a lift to Cloudsdale or back down to the ground for his job. And there aren't a lot of opportunities for laborer earth ponies in Cloudsdale that aren't hazardous or back-breaking. Even just being an earth pony in the city can be dangerous; the clouds aren't always solid underhoof."