Perhaps you could sell Parks, or other buildings to a private company, thus lowering your expenses, but also losing a proportion of your income (like anything else you'd get taxes from them), and also at a cost that in order to destroy or move buildings you'd need to pay more, because you'd need to buy the buildings back from the private companies, as well as having to buy the parks back if you wanted to edit them. It would be more realistic, things such as industrial parks, theme parks and numerous other buildings we place down are likely to be privately owned in the real world, instead of belonging to municipal government, and it could be useful if you're in the middle of a financial crisis, to sell off buildings and areas to lower expenses without loosing the benefits of having those buildings in the first place.