HOAs are voluntary. They're nutty, but people voluntary enter into those agreements. This has nothing to do with Libertarianism except in that it's free people acting freely with one another. No one's forcing you to buy a home that's part of one. I wouldn't.
HOAs are not voluntary in most cases. In some states there is no requirement to disclose the HOA prior to closing either.
Yes, an HOA can be setup as voluntary; but most are not and are part of the Land Deed that goes with the property in a clause that cannot be removed from the Deed. Fees and Fines can be placed as liens against the property (usually granted to the HOA in the Deed).
My parent's, for instance, bought a house in OH. They didn't know there was an HOA at all until months later when someone from the HOA tried to collect dues. The majority of the people in the development did not want the HOA. They couldn't absolve it unless they got the local township to annex them; and the township didn't want to annex them.
When my wife & I bought our first home in SC, they was a voluntary HOA. We never joined since the rules of the HOA only applied if you were in the HOA; and there wasn't really any benefit to being part of it. It has since dissolved because of not enough members, meetings, etc.
When we were looking for a home in GA we came across a number of HOAs, including one that was "voluntary" - voluntary until an owner joined it, then it was no longer voluntary for them or any subsequent owners. They were actively trying to get all the homes to be no longer voluntary.
When we bought our second home in GA, there was no real HOA. There is an "HOA" but it's only got charge of the maintenance for the entrance; no rules, no attachment to the deed, etc.
Both in SC and in GA we had to look long and hard to find an HOA that was not restrictive. Most had dumb rules like "you cannot work on a car in your driveway except in emergency". The worst was one in SC that had a rule that anyone under 18 found on common property after 10 PM would be arrested for trespassing - they made the rule in response to a couple of minors and an adult vandalizing the pool house.
Ultimately, HOAs do not "increase or maintain value" for a home. They decrease it because of the rules and how hard it is to change them.