This is a common practice to keep management fees to the HOA lower by bringing in revenue from buyers via document/transfer fees.
If you stop and think about it, everyone already belongs to a “homeowners association” - it’s called your City, County, State, etc. Taxes are assessed, city ordinance requires that the lawn gets mowed and with broad boundaries certain standards of maintenance and upkeep are enforced.
HOAs are just yet an additional layer of taxation, beaurarcracy and red tape yet unaccountable, it’s an end run around civic government. From what little I have read on covenant agreements they aren’t really enforceable anyway.