I looked it up and a couple of states have laws against HOAs from forcing your to have a grass lawn. Alternatives can include native plants, drought tolerant plants, xeriscaping, vegetable gardens depending on state. The states I've found are California, Colorado, Florida, Texas and Maryland, Nevada.

I don't think there's good data on exactly why but the experts view habitat loss, artificial lights at night, and pesticide use as the top three concerns (the North Americans surveyed put pesticides above light pollution but globally it was the opposite).

This is the survey of experts but is probably behind a paywall. https://academic.oup.com/bioscience/article/70/2/157/5715071