As an outsider, the concept of a "Homeowners Association" (HOA) sounds like an absolute nightmare. Are neighborhood boards really as strict and powerful as the internet makes them seem?

Living in Kenya, if you buy a house or a piece of land, you generally have the freedom to paint it whatever color you want, plant whatever you like, or park your car on your own property without asking for permission. ​But whenever I read American stories online, it seems like millions of people buy expensive houses only to pay hundreds of dollars a month to an HOA, just to have their neighbors measure their grass with a ruler or fine them because their mailbox is the wrong shade of beige. ​Do these neighborhood boards actually have the legal power to fine you for things like leaving a trash can out for too long? Why are they so incredibly common across the US if everyone seems to complain about them?