ISPs and carriers in the US have no problem deploying 5G nationwide. If only the first strand is expensive in a fiber deployment, why duplicate work by not installing residential fiber at the same time?

Also in the US, the availability of high speed, low cost fiber options versus slow, expensive copper can be accurately guessed based on nothing but the median home price in a neighborhood. When fully occupied apartment buildings lack fiber but not the townhomes across the street, "population density" is not a satisfactory explanation.