I'm going to go out on a limb and assume you've massively underestimated the true cost of installing fiber (you include no labor, or maintenance, or any equipment costs besides just the fiber for the trunk line (last mile installation is often much more expensive)), and massively overestimated the amount people in small towns are willing to pay for internet. Factor in that construction and installation in remote areas can be significantly more expensive, and the high risk that small, remote towns are likely to disappear and die over the course of 30 years, and there aren't many reasons to invest in expensive long-term infrastructure there.