>The owners of the building are sitting in the most enviable position in the economy — just by owning the asset, they will get money in the form of appreciation, from work done by other people.
You mean like a savings account? Or a treasury bond? Or stocks? Or gold? There is such a thing as opportunity cost. The money that went into buying the property, as well as the money continually spent in maintaining it (from repairs, to taxes, to insurance, to advertising for renters, to managing renters) could have been spent on something else, like an index fund - which, without any effort, could net you a nice 7% return.
You're also missing the risk profile. Property values could crash at any moment, and take all the capital along with it. It happened in 2008 to many people. Could happen again at any time. Historically, real estate hasn't been the best store of value nor provided the best rate of return on your investment.
If you think it's that easy, you should try it.