You are creating a false dichotomy. The alternative to a lawn doesn't need to be a hard paved surface -- you can have other plant life there such as wildflowers native to your locale and which survive without the massive supplements of water, fertilizer and pest control lawns often require. Such plant life has the same positive features in regard to erosion, etc. a lawn has without the downsides a mono-culture of grass often requires. Unfortunately some communities actually penalize people who don't have a lawn.