Because part of the agreement to buy the house includes agreeing to the HOA. Your neighbors have a reasonable expectation that their neighbors will abide by the community rules. If one wants to do their own thing, they should live somewhere that doesn’t come with built-in rules.
That's one of those things that sounds good on paper, as through it were plausibly true. It's not, of course, because HOAs have infected so much of new housing that they're nearly impossible to avoid unless you want to live out in the middle of nowhere.
