Ranches were popular in the 80s and 90s when US boomers were buying "forever homes".
For everywhere and everyone else, the foundation and roof are the most expensive part of the building so it makes the most sense to double or triple your square footage between those by building 2 or 3 stories.
That is not a lie and I am very much aware of that reality, as a member of my household is in serious risk to lose mobility due to health issues. Yet, vertical space is always a good thing to have.
We're not exactly packed like sardines where I live but building up, unless health issues are a concern, is always the first thing considered, exactly to save clear ground area for other uses, regardless if building on 100m2 or 10 hectares.
Where are you looking? This very well is likely regional. I grew up in the Midwest and every house in my neighborhood had at least two floors, usually more like 3 (ground floor, finished basement, 2nd story).
Communities built for older people often only have one floor due to mobility issues and parts of the country (most of the south) do not have basements. If you’re relying on film/television then it’s likely they’re not filming in the parts where basements are common.