Which is rather common in my experience. The town adjacent to the one I just moved to has a bunch of duplexes, but if you look at the current zoning it's all single-family-only. You couldn't build much of the town as it is today, which is a shame as it's very nice.

As you might expect given this, the town has steadily lost population.

Existing buildings will go up in value in an environment where construction costs are rising and the cost of replacement is increasing.