How is it exactly a retirement plan if your house goes up 200% over N years, but so do all of your neighbor's homes? You aren't changing your relative position to them.
If all homes increase in value by the same percentage, you generate a lot of cash by owning for a long time and then downsizing, or moving to a location which started out with cheaper property (historically, this is the "retire to Florida" strategy).
Or, you're going to pass on your home to your children, so it becomes part of the value of your estate. Or if you don't have any children, you can just reverse mortgage and get cash out that way. It's just like any other illiquid asset.
