Isn’t this a rare practice for communities and/or HOA’s to follow?
No. This is very common practice in homeowners associations. Most communities in this area, communities all over Colorado and the nation have common area properties that are private and for the use of the members of that community. Most homeowners associations have community pools that are private and only for the use of their members (property owners). Other communities have private clubhouses, tennis courts, lakes, sections of river, and trails. Ken Caryl has private land and trails within their community as does Pagosa Lakes, Red Feather Lakes, and Genesee, as examples.
In addition to the numerous examples of private property being off limits to people who live outside of certain communities, there are examples of “public” property that is closed to the public. Douglas County currently has a tax that funds its purchases of open space and conservation easements, as well as the building of trails within those open spaces. Some of these publicly funded spaces have restricted use of the land and trails; their trails are open to the public, but only by appointment. There may be several reasons for the restrictions Douglas County has placed on these properties, but one reason is to protect the habitat and wildlife and to minimize the impact trail use and overuse would have on the ecosystem in these properties. HRCA restricts public use because it is not publicly funded.