The government wants to make sure people have money for when they retire. They know most people won’t save enough money for retirement on their own. As such, the government takes a portion of your paycheck and saves it for you in Social Security.
HOAs essentially do the same thing. They want to make sure there’s enough money when items need to be replaced. As with retirement savings, most people won’t save enough money on their own to pay their share of replacement costs. As such, the HOA takes a portion of your monthly payment and saves it for you in the Reserve Account.
If a country has too many people that no longer can work and haven’t saved enough money, society falls apart. If a building has too many items that need to be replaced and not enough money has been saved, the building falls apart.
This is why your HOA collects money each month for items to be replaced in the future.