Kind of leaving out the real reason why they exist. Existing residents of an area don't want to pay for infrastructure for new housing developments. In the old days, a developer would build and sell a subdivision and then give the title to common areas, roads, and stuff like that to the city, and then the city would be responsible for their maintenance and repair, along with new schools, snow plow, and garbage services.

There are other reasons why existing residents don't want development, but a developer can kill the infrastructure argument by creating a HOA and have future residents fund those maintenance, repairs and services on their own.

They do it to get permits and they is why so many newer developments have them. It is a compromise for those old people complaining about traffic and paying for new schools.