If you don't have kids, I cannot think of a great reason to have a yard. Even if you do have kids, it is much better to have parks nearby. But the one benefit of the yard is that you can stick the kids there unsupervised (when they're at least 4 or so) and let them get exercise on a swing set or playhouse while they're still within yelling distance, as opposed to having to escort them several blocks away to a park.
Otherwise, I don't see the point. I think it's great to have areas to put plants and maybe grow some vegetables, but you don't need a "yard" to do that, just some planter boxes and/or some patio space for containers. Smaller spaces are easier and better to make aesthetically pleasing than sprawling yards. And as others have pointed out, large yards are a maintenance headache. There are few things less sensible than vast areas of grass that have to be mowed every week and that serve no function other than just to be there.